Refactor syntax for accessing custom metadata

• Fixes connection creation and associated validations

• Adds further connectors (with icons)

• Adds SQL parser endpoint

• Add Lineage list API and integration tests

• Fix bug on locking custom metadata

• Refactor syntax for accessing custom metadata properties

  Previously the custom metadata property First Name would have been accessed as follows:
  cm.first_name

  This could cause confusion how the name was converted so now the following syntax will be used:

  cm['First Name']