Made framework name configurable

* Framework name can now be overridden.
* By default, the framework name is still 'Jenkins Framework', for
  backward compatibility reasons.
* Making framework name configurable helps in environments, where there
  are multiple Jenkins Master/Jenkins Schedulars running against common
  mesos.
* Update .gitignore files
Merge pull request #14 from mohitsoni/master

Making framework name configurable.