Connect Ecore-Creation service via socket

[CamilleLetavernier]

Original issue from the archived repo: eclipsesource/ecore-glsp#78

Like mentioned in eclipsesource/ecore-glsp/issues/64 it would be nice if the ecore-file generation service would be called via socket from the theia backend.

Additionally there could be a better solution for finding the jarPath. Right now it checks wheter or not the current OS is Windows and then cuts the first char of the path string to enable the feature

More generally, we should provide an "Ecore Backend" Java plug-in, that should expose a JSON RPC endpoint (Similar to what already exists for the Ecore GLSP Server). The Ecore Backend will provide the following actions:

Create a new model (Ecore File)
Create a new GenModel
Generate code from the GenModel
...
Then we don't have to worry about the jarPath anymore