Refactoring: one GerritHandler instance that handles multiple GerritConnections.

Add isServerInteresting check in GerritTrigger.
Remove unused serverName field in GerritProject.

Change-Id: I938d199e542f06c9fc7d3b50615618ae7f2a6fc9
Move initializeProvider to isServerInteresting.

Remove repetitive code.

Change-Id: I0745ad89702f26abe0d6154230487a8b1b936277
Merge pull request #91 from mathieu-wang/one-gerrit-handler

Refactoring: one GerritHandler instance that handles multiple GerritConn...