Cleanup and test of garden connection configs

[jlrpnbbngtn]

Testing

This PR accomplishes two main goals:

1. to_brewtils now correctly processes systems associated with a garden via an update to make_object of GardenSchema in garden_schema.py. The unit test in test/db/schema/garden_schema_test.py demonstrates this.

2. The functions that manipulate gardens in garden.py now call a function clean_garden_connection_params at points where the garden is inserted or retrieved from the database. This function only cleans up the garden connection parameters and passes the rest of the garden through untouched.

   This addresses the problem where a user upgrades to code that includes the garden schema but the database in the existing system may have gardens where the connection parameters are squirrely (and would therefore fail validation).

   There are comprehensive units tests to cover all of the possible permutations of connection parameters, explained further below.

The unit tests for the connection parameters fall along three main lines: the garden.connection_type is one of LOCAL, HTTP or STOMP. The tests thus verify each of the following cases is handled correctly:

1. LOCAL
   a. no connection params
   b. connection params that are not empty
2. HTTP
   a. good http, empty stomp
   b. good http, no stomp
   c. good http, bad stomp
   d. bad http, no stomp
   e. bad http, good stomp
   f. bad http, bad stomp
   g. no http, no stomp
   h. no http, good stomp
   i. no http, bad stomp
3. STOMP
   a. empty http, good stomp
   b. no http, good stomp
   c. bad http, good stomp
   d. no http, no stomp
   e. no http, bad stomp
   f. good http, bad stomp
   g. bad http, bad stomp

The unit tests are tedious and repetitive (it would have taken too long to refactor them to make them simple and elegant for no real benefit), but they should cover all the combination of connection types and connection parameters.

[jlrpnbbngtn]

Here starts the code to cleanup bad connection configuration in Gardens (many of the changes in this file are related to renaming brewtils objects).