Autocomplete suggestions with states and `(this)`

[CatarinaGamboa]

Why

When writing the state refinements it is helpful to have shortcuts to write the state we intend.
Therefore, the vscode extension has to work together with liquidjava so that it could provide a list of states that the server can use to send when an autocomplete request arrives.

This issue involves this repo and liquidjava.

Steps

1. In vscode-liquidjava check the type of information required by the autocomplete invocation.
2. Currently, liquidjava (as server) is invoked through CommandLineLauncher.launch(...) from the vscode-liquidjava and it returns only ErrorEmitter with information for identifying and reporting the error message. The return should be changed to another object that includes the error message and additional information.
3. This additional information should include the states for each class so that they can be retrieved from the vscode-liquidjava side and sent to the client editor.

[alcides]

It would also be interesting to only provide this autocomplete when the cursor is inside a refinement.