Added tests for ModuleInstaller.

Test that a mod can be installed in a clean KSP instance.
Test that a mod can be removed after installation.
Test that ModuleInstaller instances are decoupled when working on multiple KSP instances.
Decoupled ModuleInstaller instances based on KSP instance GameDir.
Merge pull request #33 from AlexanderDzhoganov/master

Added Headless property to IUser
Tests for RelationshipResolver with version support.
Merge pull request #35 from AlexanderDzhoganov/master

Small fix to without_enforce_consistency
Merge pull request #36 from AlexanderDzhoganov/master

Added enforceConsistency flag to RegistryManager.Save
Merge pull request #34 from Ormira/versions_#17

Tests for RelationshipResolver with version support.
Merge pull request #31 from mgsdk/refactor_singleton_moduleinstaller

Refactor ModuleInstaller.GetInstance() singleton, decouple instances
Merge remote-tracking branch 'upstream/master'