Merge pull request #1 from AxelBehrens/version-env-variable

provide vault folder version in environment variable
enhance robustness agains changes in VaultSCMRevisionState
Merge branch 'folder-version-for-update-checking'
polling and checkout is now based on folder versions instead of build dates
Merge branch 'master' of https://github.com/jenkinsci/vault-scm-plugin
fixed GETVERSION syntax
switch method to pass vault folder version from wrongly used build environment to build actions and added some logging
Merge branch 'folder-version-for-update-checking'