Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
{
    registerFunctionCurrentDatabase(factory);
    registerFunctionCurrentUser(factory);
    registerFunctionCurrentProfiles(factory);
    registerFunctionCurrentRoles(factory);
    registerFunctionHostName(factory);
    registerFunctionFQDN(factory);
    registerFunctionVisibleWidth(factory);
    registerFunctionToTypeName(factory);
    registerFunctionGetSizeOfEnumType(factory);
    registerFunctionBlockSerializedSize(factory);
    registerFunctionToColumnTypeName(factory);
    registerFunctionDumpColumnStructure(factory);
    registerFunctionDefaultValueOfArgumentType(factory);
    registerFunctionDefaultValueOfTypeName(factory);
    registerFunctionBlockSize(factory);
    registerFunctionBlockNumber(factory);
    registerFunctionRowNumberInBlock(factory);