safety net checkpoint for coordinator, kinda backup
Client ssh library is reorganized
  - several bugs are fixed
  - several new classes are introduced
  - parallel execution of SSH commands are made more solid
  - related changes in webapp coordinator
Merge pull request #57 in CHOP/main from coord-safetynet to master

* commit '8db93a54bb0753fecee6da44122c3f3e20f924d3':
  Client ssh library is reorganized   - several bugs are fixed   - several new classes are introduced   - parallel execution of SSH commands are made more solid   - related changes in webapp coordinator
  safety net checkpoint for coordinator, kinda backup