Autocomplete openable classes

[echebbi]

Current behavior

The Xtext editor's autocomplete does not suggest anything after typing open class.

Desired behavior

The editor autocompletes with the name of available EClass.

Example

Given (| represents the cursor):

open class |

Hitting CTRL+Space would show available EClass intances, and completes the code when the user selects one:

open class HelloWorld {

    |

}