Added support for parameterized manual jobs

This is needed to fully support the [Build Pipeline Plugin](https://wiki.jenkins-ci.org/display/JENKINS/Build+Pipeline+Plugin)

Change-Id: Ie830696bc6207df5d3766058d1a71c98b01470d0
fixed tests, Groovy with blocks are not executed in then sections, Specification.with has to be used, see http://spock-framework.3207229.n2.nabble.com/with-closure-inside-a-then-block-does-not-execute-td7518019.html
remove multiscm limit
Merge pull request #197 from CoreMedia/multiscm

Removed multiscm limit
Update README.md
Merge pull request #198 from joshua-jandyco/master

Fix typo in README.md
removed TODOs

most things are OK as they are, other things will come back as issues or pull request if there really is something broken or missing
Added parameters closure inside BuildPipelineTrigger

Change-Id: I52ddf5a10977770b935401a256b90716bc3cbaf7
avoid deprecated API
removed dead code
Merge pull request #200 from CoreMedia/cleanup

Removed TODOs
Merge pull request #202 from jenkinsci/dead-code

Removed Dead Code
cleanup
Improve Exception message for missing workspace files
Merge branch 'deprecations'

Conflicts:
	job-dsl-plugin/src/main/groovy/javaposse/jobdsl/plugin/JenkinsJobManagement.java
Merge branch 'build-trigger-parameters'
added release notes entry and a test
Merge branch 'JENKINS-23006'
Revert BuildParameterHelperSpec test
merge