[JENKINS-11677] only use the label field if the parameters in it resolve to something non-empty
Merge branch 'master' of github.com:jenkinsci/perforce-plugin
fixing problem with labelling when using client spec from file
[FIXED JENKINS-11740] fixing typo
[maven-release-plugin] prepare release perforce-1.3.5
[maven-release-plugin] prepare for next development iteration
[JENKINS-11786] adding parameter substitution support to password field
[JENKINS-11840] replace all spaces with underscores in client spec
fixing potential issue with last commit
[FIXED JENKINS-11878] fixing NPE during polling

this particular NPE seems to be possible when the user switches an existing build to perforce, and attempts to use polling before executing the build at least once.
[FIXED JENKINS-11893] adding global env variables to config substitutions
[maven-release-plugin] prepare release perforce-1.3.6
[maven-release-plugin] prepare for next development iteration
[JENKINS-12202] adding substitution support for exclude User/Files fields
Add streams support
Fixed unit test cases.
fixing issue where the list of changes includes pending ones
[maven-release-plugin] prepare release perforce-1.3.7
[maven-release-plugin] prepare for next development iteration
Merge branch 'stream' of git://github.com/miktap/perforce-plugin into stream