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**Apache Airflow version**: 1.10.11


**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**:

- **Cloud provider or hardware configuration**: 
- **OS** (e.g. from /etc/os-release): Windows 10 WSL (Ubuntu18.04.4)

- **Kernel** (e.g. `uname -a`): Linux DESKTOP-8IVSCHM 4.4.0-18362-Microsoft #836-Microsoft Mon May 05 16:04:00 PST 2020 x86_64 x86_64 x86_64 GNU/Linux
- **Install tools**:
- **Others**:

**What happened**:

In the __Trigger Dag__ view for a specific Dag, the view asks for JSON formatted object as inpunt. 
In the __Dag Runs__ view (list), it shows python formatted object in the __Conf__ column.

Despite JSON and Python formating being quite similar they differ in respect to string quotation marks: json uses double-quotes(") and python uses single quote(').
This makes annoying to copy a previously used config to a new trigger.

<!-- (please include exact error messages if you can) -->

**What you expected to happen**:

I would expect a consistent read/write of Dag Run configuration. 
In particular require a Json in the Trigger Dag view, and display a Json in the DAG Runs view.

**How to reproduce it**:
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--->

1. Trigger a DAG manually passing a Json dict `{"test": "this is a test"}`.
2. Go to Dag Runs view, it shows as `{'test': 'this is a test'}`


**Anything else we need to know**:

This is not application breaking issue, more a quality of life/usability issue. 
I imagine it would be a minor change and could be tagged as an first issue

tests/www/test_views.py
self.logout()
        self.login(username='test',
                   password='test')
        test_role = self.appbuilder.sm.find_role('dag_acl_tester')
        perms = {str(perm) for perm in test_role.permissions}
        self.assertIn('can dag edit on example_bash_operator', perms)
        self.assertNotIn('can dag read on example_bash_operator', perms)
    def test_index_success(self):
        self.logout()
        self.login()
        resp = self.client.get('/', follow_redirects=True)
        self.check_content_in_response('example_bash_operator', resp)
    def test_index_failure(self):
        self.logout()
        self.login()
        resp = self.client.get('/', follow_redirects=True)
        
        self.check_content_not_in_response('example_subdag_operator', resp)
    def test_index_for_all_dag_user(self):
        self.logout()
        self.login(username='all_dag_user',
                   password='all_dag_user')
        resp = self.client.get('/', follow_redirects=True)
        
        self.check_content_in_response('example_subdag_operator', resp)
        self.check_content_in_response('example_bash_operator', resp)
    def test_dag_autocomplete_success(self):