Support keybinding toggle for line comment

**Is your feature request related to a problem? Please describe.**
On the client, using ctrl+/ to toggle line comment does nothing. Works for non-codetogether files on the client in Eclipse and IntelliJ.

**Describe the solution you'd like**
Support ctrl+/ to toggle line comments on CodeTogether files in all client IDEs

**Describe your primary environment**
Eclipse and IntelliJ

