* add git-revision-webpack-plugin
* configure git-revision-webpack-plugin
* add commit to footer
* rename version and commit to backendVersion and frontendVersion
* rename version and commit to backendVersion and frontendVersion
* disable lint error due to use of globals
* fix snapshot test
* read frontend version from VERSION file instead latest git revision
* directly require from version.json file instead of going through WebPack's DefinePlugin
* run snapshots
