Add eclipse specific files to gitignore
Fix NPEs during MR checks

* The first NPE occurred when the _mergeRequestStatus was not set for the merge request wrapper
* The second NPE occured when the merge request wrapper was trying to determine whether a MR job should be invoked.
  MR on gitlab which are stalled would cause NPE's since the lastest commit could not be determined.
  The plugin will now skip the run for these MRs.
Improve plugin setup guide.
Updated Jenkins version dependency

* Set the dependency on Jenkins to the latest LTS version
Merge pull request #74 from dinosaurjr10/feature/use-lts-version

Updated Jenkins version dependency
Merge pull request #73 from Jotschi/bugfix-issue-60

Bugfix issue 60
Add regex that allows a job to only be executed for specific branches

I customized the GitlabBuildTrigger and added a new field in which the user can specify a regex.
This regex is used in the GitlabMergeRequestWrapper to decide whether the job should be executed or not.
The target branch name will not be checked using the regex when no regex has been defined in the trigger field.
Merge pull request #75 from Jotschi/enhancement-38

Add regex that allows a job to only be executed for specific branches
Add logging to make build decision transparent
Add normalization when comparing usernames