[BI-1157] Allow for imports to not be connected to a program

[ctucker3]

• Changes the importer_mapping table in the database to remove the program_id.
  • Adds a new table importer_mapping_program that now stores the import to program connection
  • System imports do not have a program attached and is how they are identified as system imports.
• Adds an endpoint to get system imports.
  • The endpoint allows searching by import name.
  • Program import queries were modified so they do not grab system imports.
• A check was added in the create mapping endpoint so that program mappings don't use the same name as system mappings.
• For saving data, all of the endpoints are the same.
• Added tests for system mappings that also acts to test the same machinery that the program mappings use.
  • Creation of program mappings are also covered in the tests.

[nickpalladino]

What? Importer tests?

[ctucker3]

Hahah yeah I was feeling ambitious that day :P