[plug-in][languages] Provide code diagnostic support to languages

[ashumilova]

Need to provide the support of managing the code diagnostic, which indicate issues with the code. It includes following event:

• onDidChangeDiagnostics - event that is fired when diagnostics change with the list of resources, where it happened
  and methods:
• getDiagnostics - returns all diagnostics for the pointed resource
• createDiagnosticCollection - for creating new diagnostic collection

A diagnostics collection is a container that manages a set of diagnostics, that are always scopes to the diagnostics collection and a resource.

Documentation

[mmorhun]

Done