make public-but-protected config settings unprefixed

Since these settings are not internal, but supposed to be user editable
via the config - name them without an underscore prefix
add the key to callback methods

This necessitates changing the test methods as they don't expect to
receive the key
You can now change a specific key's value

Add a test demonstrating it works
store the path in keys
pass the path to the recurse method
Merge pull request #91 from FriendsOfCake/feature/api-transform-cleanup

make public-but-protected config settings unprefixed
Fixes indirect modification has no effect error.

Also adds some tests to prevent it from happening again.
Goddamnit Yoda, I told you not to touch my pc.
Optimization of ApiFieldFilterListener::_checkField().
Updated travis config
Replaces array_search() for in_array().
Merge pull request #97 from Phally/fieldfilter

Some love for the ApiFieldFilterListener