Implemented the "AssembliesDirectory" configuration option to specify where the internal assemblies will be extracted to.

This was previously not possible, so I thought, yeah, let me just do it by myself.
There's now a new setting *Raven/AssembliesDirectory*.
I also ran the tests, and they all seemed fine, although I'm not really familiar with the way costura works, so you propably should try it by yourself.

**Note**
I needed to move the *GetExtractedAssemblyLocationFor* method from the *AssemblyHelper* class to place where I have access to the *InMemoryRavenConfiguration*.
So I moved this method to the *AssemblyExtractor* class.

I will propably send you the copyright assignment agreement tomorrow.

Relevant mailing list thread:
https://groups.google.com/forum/#!topic/ravendb/d_lGhyCfRMA