Add AssemblyCopyMode to RemoteDomainExpression

* Add an optional enum to RemoteDomainExpression to change how copying
  assemblies works. The default is still the copy once behavior, but you
  can now set the AssemblyCopyMode to Always if you need the latest
  required assembly each run.
* Add tests to the BigRemoteServicesIntegrationTester for both the
  default and copy always behavior.
Re-add Move(string directory) to AssemblyRequirement

* To maintain API compatibility re-add the Move(string directory) method
  and default it to using AssemblyCopyMode.Once.
AssemblyRequirement tracks own AssemblyCopyMode

* Remove Move(string, AssemblyCopyMode) now that AssemblyRequirement
  tracks its own copy mode when constructed.
* Add additional constructors to specify AssemblyCopyMode, the original
  two now default to the "Once" copy mode
* Add additional RequireAssemblyXYZ overloads to have an
  AssemblyCopyMode
* RequireAssemblyXYZ methods without AssemblyCopyMode defer to the
  AssemblyCopyMode on RemoteDomainExpression
Merge pull request #103 from DarthFubuMVC/remoteDomainExpressionCopyMode

Remote domain expression copy mode