Removed the v1 REST API

- Moved AppDefinition to mesosphere.marathon.state
- Moved Command to mesosphere.marathon.state
- Moved MarathonExceptionMapper to mesosphere.marathon.api
- Necessary import modifications
- Fixes #404
Added missing file
Rebase with master
Removed help endpoint content for v1 API
Purge v1 from README, REST, template
Merge pull request #434 from mesosphere/issue-404-remove-v1

Removed the v1 REST API