Improving model host paradigm, model handlers refactoring

[avishnyakov]

CSOM provisioning requires more complex "model hosts".

For some cases, instead of having just Web/List instance, more variable are required - for SP2013 workflow, security and content type links.

This requires to create and pass "model host" as a complex object to the model handlers.
In turn, re-factoring is required:

1. Finish CSOM model hosts

2. Refactor CSOM model handlers

3. Implement complex model hosts for SSOM

4. Refactor SSOM model handlers

5. Finally, refactor ModelHandlerBase class "DeployModel(object modelHost, DefinitionBase model)" method with "DeployModel(object modelHost)" signature supposed to consume only CSOMModelHostBase/SSOMModelHostBase classes with "complex" variables and contexts

[avishnyakov]

Model hosts also should allow to start provision from particular node, et List or ContentType.

[avishnyakov]

Adding SiteModelHost/WebModelHost for SSOM. This should be enough for the start.