Add support for remote code coverage. This branch still needs a few details to work when not requesting code coverage.
Ignore code coverage artefacts.
Merge branch 'master' into coverage
Add tests for queries.
Remove unused method Datachore\Model::getKey.
FIX: setting values for filters for boolean and timestamp values.
Removing unused code for OR operator (still unsupported by Google Datastore).
Add new local tests and supporting files:

  * Patch for GAE SDK to expose remote api environment variables.
  * Add /remoteapisettings call to front controller to get the remote api settings.
  * tests/DatastoreLocalTest.php (which connects to remote api directly)
Get tests to work without code coverage (allow enabling/disabling coverage remote).
Ignore untestable code in code coverage.
Add code to front controller for enabling/disabling code coverage remotely.
Remove call to all from /test/query in the front controller.
Merge branch 'coverage' into localtests

Conflicts:
	tests/frontcontroller.php

Minor overlapping conflicts.
Support null values and unset properties.
FIX: make support for timestamps *almost* fluid.
Run the new local tests on travis.
Add support for coveralls.
Enable remote PHP debugging (for code coverage).
Add some debugging to find out why coverage does not work on travis.
Make log dir in before_script.