OmniSharp plug-in

[ThatRendle]

Provide a completion "recommender" plug-in for omnisharp-roslyn, to suggest table/column/proc names from database schema.

Probably prescribe a simple.data.config.json JSON file along the lines of

{
  "completion": [
    { "default": { "connectionString": "data source=..." } }
  ]
}

Waiting on OmniSharp/omnisharp-roslyn#208