Add a class to store automerge configuration

Add a class to store automerge configuration.

Signed-off-by: Francois Visconte <f.visconte@criteo.com>
Add AtomicityHelper class

This class add some helper to check dependencies between changes
and there atomicity.
Add a utility class to update a review

This class is used to set a review label or set a comment.
Rename qabot variable to bot.

qabot is somewhat criteo-specific. Name it bot instead.
Add a way to retrieve a comment from a file.

Retrieve review comment from files stored in gerrit etc_dir.
Add AutomaticMerger logic

Automatically merge mergeable reviews that are on the same atomic topic
Simplify a bit commenting from template file.

Directly pass template filename to setMinusTwo and commentOnReview.
Fix Guice binding

Bind correct classes to allow guice to instantiate class attributes.
Fix unit test according newly added constructor parameter