Fix to help with the changelog for a PR build.

This adds a BuildData as an Action for a build that represents the last
build for this particular PR.  This ensures that GitSCM uses the
appropriate revision when determining the changelog.
Fixes issue where we are unable to get the author email on triggers

Sometimes the GitHub API throws a NPE when attempting to get the user for
a PR; this information is optional and shouldn't cause the trigger to
fail.
Update GhprbTrigger.java

Just spent some time tracking down the cause of this issue which started appearing after someone had disabled the GitHub plugin. The wording change will make the cause of this issue clearer to the user to allow for a quicker resolution.
- when using a repo from an organisation the owner.login field is null. Try to fetch the owner name from html_url instead which doesn't rely on the owner object - fixes exception and issue #18365
- fix isUserMemberOfOrganization method by using the org.hasMember method instead of iterating over the members array (the latter didn't seem to return all members of an organisation in some circumstances)
- check if a pr is mergable on comment aswell - not only on pull request creation. Fixes building of the merged pull request when triggered by comment
- fix some logging spam and prevent unneeded exceptions
Fixed a typo
"ghprbPullLink" - Added capturing the link to original Pull-Request so that the Jenkins Job can "link-back" to the Pull-Request on GitHub that actually triggered the Job in the first place

"ghprbSourceBranch" - Added capturing "source-branch" name in a Pull-Request (since it would contains information like Ticket Number which is essential for integration with Tracking Systems (like JIRA, RALLY, BUGZILLA etc…)

Sample Source-Branch name "Bug1234-nirav-fix-issue-abcd" this allows to update the ticket with ID-Bug1234 stating that a PR was opened for this ticket
Issue #100: ability to include log details in commit comments
Merge pull request #88 from valdisrigdon/handle_owner_email_npe

Fixes issue where we are unable to get the author email on triggers
Merge pull request #99 from Mailaender/patch-1

Fixed a typo
use the StringBuilder for whole message
Do not change behaviour without notice. Set default to not use logExcerpt
Merge branch 'logExcerpt'
Merge pull request #15 from Memphiz/loggingspam

- fix some logging spam and prevent unneeded exceptions
fix forgotten variable change and logging
Merge branch 'fixorganisation'
Merge pull request #16 from Memphiz/mergedprtrigger

- check if a pr is mergable on comment aswell - not only on pull request...
Merge remote-tracking branch 'valdisrigdon/changelog'
remove unused imports

Conflicts:
	src/main/java/org/jenkinsci/plugins/ghprb/GhprbBuilds.java
	src/main/java/org/jenkinsci/plugins/ghprb/GhprbTrigger.java