address some SpotBugs warnings

[danthe1st]

I have run a SpotBugs analysis on the code and addressed a few issues:

• closing resources with try-with-resources blocks
• using Statements instead of PreparedStatements where no parameters where used
• making a mutable public variable private and using a getter
• removing unused code
• adding queue() to some RestActions
• removing catching of exceptions in tests if these exceptions would be issues with the test instead of issues with the actual code

Not addressed:

• deferencing of possibly nullable expressions that shouldn't be null anyways
  • e.g. a.b() == null ? "" : a.b().c()
• non-applicable SQL injections in code that is supposed to allow administrators to access the DB (e.g. migrations)