Add basic logging functionality.
Merge branch 'master' of https://github.com/ZocDoc/ZocBuild.Database

Conflicts:
	ZocBuild.Database/Build/DatabaseManager.cs
	ZocBuild.Database/DependencyWalking/DatabaseStateWalker.cs
Merge branch 'master' into NET_40

Conflicts:
	ZocBuild.Database/DependencyWalking/DatabaseStateWalker.cs