Implement integration tests.

Provide intergation testing for the git-review utility. Requires
Gerrit war file (like 2.6.1-gerrit.war) in the .gerrit directory in
the git-review project (like git-review/.gerrit/2.6.1-gerrit.war).

Tests start local Gerrit and create test user and project there to
be used.

Closes-Bug: 1048724
Change-Id: I3242479dcbcf230085178004540992680f3f8e30