[FIXED JENKINS-18937] Add dsl method to add timestamps. Packed this into a buildWrapper block.
[FIXED JENKINS-18937] Add dsl method to add timestamps. Packed this into a wrapper block.
Add other environment methods on TopLevelHelper to EnvironmentContext with a method delegating to it on EnvironmentContextHelper
Rename environment -> wrapper
Merge branch 'master' into timestamper

Conflicts:
	job-dsl-core/src/main/groovy/javaposse/jobdsl/dsl/helpers/TopLevelHelper.groovy
	job-dsl-core/src/test/groovy/javaposse/jobdsl/dsl/helpers/TopLevelHelperSpec.groovy
remove delegating methods from wrapperHelper
Merge pull request #73 from wolfs/timestamper

JENKINS-18937: Add dsl method to add timestamps