teamcity basic support


FR http://feedback.gitlab.com/forums/176466-general/suggestions/4139027-teamcity-integration

[This is a clone of https://github.com/gitlabhq/gitlabhq/pull/7570, because of a pull request bug.]

Simple Teamcity integration for MergeRequest build status and link on a build.

Algorithm: get status of the last build in Teamcity for concrete Teamcity.BuildConfiguration_ID and MergeRequest.SourceBranch and MergeRequest.Commits.Last
Have to create a build configuration Teamcity.BuildConfiguration_ID to trigger build on each push.
Have to create a survice user and give him viewer-access rights on Teamcity.BuildConfiguration_ID.

Algorithm is very simple but it is working for us since 2014/07/15 and everybody happy :-)
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