Common platform for all IDE plugins

Having IDE plugins for most popular IDEs to autocomplete templates and validate application would be very nice.

This issue depends on [other issue](https://github.com/aurelia/tools/issues/31), that would provide among other things a common tooling library for IDEs to analyse the application statically. If that library is build with keeping in mind this issue (IDE plugins), then building IDE plugins would become way less complicated.

If I'd have to build a common platform for IDE plugins, I'd probably create a background process with REST API, that can be started by IDE plugin. Then all IDE plugins could be implemented relatively easily on top of the REST API to execute different commands (autocomplete, validation, ...).

As i understand, the library should build and provide some kind of application model, that IDE could use to query for example view and custom element models that contain information about template that is used by it and methods/fields, bind. When this information is available, plugins could easily implement
- autocompled/intellisense
- fields and methods in binding expressions
- to import/require custom elements/css files into html template.
- validation (see what has been mentioned [in the other issue, that proposes build-time validation](https://github.com/aurelia/tools/issues/31).
- wizards for
- new project
- new view's
- new custom elements, attributes, value converters and maybe more

I'd personally like to have a plugin for Atom and Eclipse IDEs. When Aurelia provides the common tooling library for IDEs, i think i could come up with very primitive Eclipse plugin myself.

Start by reading the dependent issue 31 and its proposal for a shared static-analysis tooling library. Then evaluate the suggested background process and REST API alongside the application model, autocomplete, validation, and wizard goals; this issue needs an agreed architecture and scope before implementation can be considered done.

Written by the indexing model from the issue text.