Add CodeReview vote ability to the Gerrit trigger

- Made all four of the
  gerrit-build-(successful|failure)-(verified|codereview)-value
  parameters optional, so you can override only the ones you want.

- Also allows for vote values like '+1' in the yaml by first coercing
  to int and then str.

Change-Id: Id2ad7e4a4cf53bd33b3aca80fd95ed1d4b3ff266
New base class to declare test cases and tests to the node option

This patch refactors the tests suite to use a base class to declare test cases
just using a class declaration, the existing test class was modified to use it
and new tests are using it as well.

These tests verify the XML generated when the 'node' option is set and
when it's absent.

Change-Id: Iddcdd63e0ab7c459f6513b1d1ebf19e19a362c1d
Added support for Git shallow clone parameter

Change-Id: Ia0251f25ff22fff10fe53ba6bf54f0e9072210fd
Updated gitblit projectname

Change-Id: I373841676bc48c8531761af5fcc5192913262552
Merge "Add CodeReview vote ability to the Gerrit trigger"
Merge "New base class to declare test cases and tests to the node option"
Merge "Added support for Git shallow clone parameter"
Merge "Updated gitblit projectname"
Fix string continuation exception

Python does not concatenate strings before performing
substitutions. Make sure that python sees the error message
as a single string.

Change-Id: Ib0561f93c76239b93000885250b3fa15ccaeb937