First experimental version of the promotions
Experimental PromotionsContext
PreDelete
Merge branch 'promotions' of https://github.com/denschu/job-dsl-plugin
into promotions

Conflicts:
	job-dsl-core/src/test/groovy/javaposse/jobdsl/dsl/helpers/PromotionsHelperSpec.groovy
	job-dsl-core/src/test/resources/promotions.dsl
conditions