eis

Merge pull request #11 in EIS/eis from develop to master

* commit '099385bab26b99f2bfaf08120c8e66fb7ef16763':
  EISNG-90: Added helper script to determine Git branches
  Updated checksum
  EISNG-90: Updated readme regarding Jenkins setup
  EISNG-90: Updated readme regarding Jenkins setup
  EISNG-90: Updated release build script according to separated preparation steps and added function comments
  EISNG-90: Added function comments and updated error codes
  EISNG-90: Implemented merge back to source branch and update pkgrel for next development iteration
  EISNG-90: Cleanup preparation script
  EISNG-90: Copied preparation script as base for real release build script
  EISNG-90: Renamed script as it performs only release preparation steps
  EISNG-90: Fixed order of function calls; Implemented handling of updated APKBUILD file
  EISNG-90: Improved environment check and implemented next steps towards new release build behaviour
  EISNG-90: Implemented merge to master and determination of release version entries to use
  EISNG-90: Updated helper functions
  EISNG-90: Renamed helper script and setup new function skeletons
  EISNG-90: Renamed helper script
  EISNG-90: Updated parameter evaluation
  EISNG-90: Added more checks for necessary env vars and improved determination of alpine base version