##### SUMMARY
As a nicety to the user, `ansible-galaxy collection` should check certain properties of the `collection_name` argument, and provide helpful suggestions about expected format.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
lib/ansible/galaxy/collection.py

##### ADDITIONAL INFORMATION
When getting this message, it's not clear to the user what they should do differently:

```yaml
$ ansible-galaxy collection install chrismeyersfsu_tower_modules -p alan -vvv
ansible-galaxy 2.9.0.dev0
  config file = None
  configured module search path = ['/Users/alancoding/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/alancoding/Documents/repos/ansible/lib/ansible
  executable location = /Users/alancoding/.virtualenvs/ansible3/bin/ansible-galaxy
  python version = 3.6.5 (default, Apr 25 2018, 14:23:58) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
No config file found; using defaults
Opened /Users/alancoding/.ansible_galaxy
 [WARNING]: The specified collections path '/Users/alancoding/Documents/repos/jlaska-ansible-playbooks/alan' is not part of the configured Ansible collections paths
'/Users/alancoding/.ansible/collections:/usr/share/ansible/collections'. The installed collection won't be picked up in an Ansible run.

Found installed collection chrismeyersfsu.tower_modules:0.0.1 at '/Users/alancoding/Documents/repos/jlaska-ansible-playbooks/alan/ansible_collections/chrismeyersfsu/tower_modules'
Processing requirement collection 'chrismeyersfsu_tower_modules'
ERROR! Unexpected Exception, this is probably a bug: not enough values to unpack (expected 2, got 1)
the full traceback was:

Traceback (most recent call last):
  File "/Users/alancoding/Documents/repos/ansible/bin/ansible-galaxy", line 111, in <module>
    exit_code = cli.run()
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/cli/galaxy.py", line 269, in run
    context.CLIARGS['func']()
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/cli/galaxy.py", line 617, in execute_install
    no_deps, force, force_deps)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 450, in install_collections
    force, force_deps, no_deps)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 831, in _build_dependency_map
    validate_certs, (force or force_deps))
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 898, in _get_collection_info
    parent=parent)
  File "/Users/alancoding/Documents/repos/ansible/lib/ansible/galaxy/collection.py", line 296, in from_name
    namespace, name = collection.split('.', 1)
ValueError: not enough values to unpack (expected 2, got 1)
```

Instead of `ValueError`, it would be better to give text like

> Improperly formatted collection name argument. Collection name must be of the format "username.collection_name", like "chrismeyersfsu.tower_modules"

display.display("Publishing collection artifact '%s' to %s" % (collection_path, server))
    n_url = _urljoin(server, 'api', 'v2', 'collections')
    data, content_type = _get_mime_data(b_collection_path)
    headers = {
        'Content-type': content_type,
        'Content-length': len(data),
    }
    if key:
        headers['Authorization'] = "Token %s" % key
    validate_certs = not ignore_certs
    try:
        resp = json.load(open_url(n_url, data=data, headers=headers, method='POST', validate_certs=validate_certs))
    except urllib_error.HTTPError as err:
        try:
            err_info = json.load(err)
        except (AttributeError, ValueError):
            err_info = {}
        code = to_native(err_info.get('code', 'Unknown'))
        message = to_native(err_info.get('message', 'Unknown error returned by Galaxy server.'))
        raise AnsibleError("Error when publishing collection (HTTP Code: %d, Message: %s Code: %s)"
                           % (err.code, message, code))
    display.vvv("Collection has been pushed to the Galaxy server %s" % server)
    import_uri = resp['task']
    if wait:
        _wait_import(import_uri, key, validate_certs)
        display.display("Collection has been successfully published to the Galaxy server")
    else:
        display.display("Collection has been pushed to the Galaxy server, not waiting until import has completed "
                        "due to --no-wait being set. Import task results can be found at %s" % import_uri)
def install_collections(collections, output_path, servers, validate_certs, ignore_errors, no_deps, force, force_deps):