PR with initial SSH support implementation - https://github.com/eclipse-che/che-server/pull/539 
There are a few enhancements that need to be done as part of this issue:

• [x] if SSH URL points to the unsupported provider and che-server can not retrieve devfile, workspace should be started based on the default one (appropriate warning message should be shown on the workspace startup screen)
• [x] default devfile should be also used if SSH url points to the supported provider, but devfile still can not be retrieved (e.g. private repo, no OAuth / PAT are configured)