Bootstrap doc for orchestration.

A mail application is used as exampel.
Bootstrap mail sample.
Add dependencies (Handlebars and loader.)
Use handlebars as template engine.
Add module stubs.
[Mail sample] Submodules are connected in the initialize method.
Services `use` and `dispose` receive `moduleid` as 3rd arg.
Routing service use moduleid as url prefix by default.
Mail sample has dedicated services file.
sample mail relies on service declaration.
Enhance mail sample modules.
[Mail] add sample data.
Enhance conversation module.
Folder module handles collection fetching.
Reuse Conversation module in several places.
Add conversation colection.