Allow for changes to workspace RAM to existing workspace

[bmicklea]

Today there is no way in the UI to change an existing workspace's RAM allocation.

Reproduction Steps:

1. Create a workspace with 2GB RAM
2. In the user dashboard you can see the 2GB RAM allocated in the workspaces view
3. Clicking into the workspace details doesn't let you see or change the workspace RAM allocation

Expected behavior:

It would be ideal if in the workspace details view you could change workspace RAM allocation.

Observed behavior:

Can't change RAM.

Che version: 4.5.0
OS and version: Used SaaS at codenvy.com
Docker version: Used SaaS at codenvy.com
Che install: Used SaaS at codenvy.com

Additional information:

Problem has happened with all versions of Che and is consistent.