Naming changes, some refactoring

In preparation for placing this module into a new public repository,
I've made the following changes to module and command names:

Renamed module from PSLogging to PowerShellLogging , to avoid the PS
prefix per Microsoft's recent posts.

Renamed Add-LogFile and Add-OutputSubscriber cmdlets to Enable-LogFile
and Enable-OutputSubscriber instead, so they match up better with the
Disable-* cmdlets.

Some minor code changes (removed unnecessary "this" references, etc.)
Merge branch 'master' of https://github.com/dlwyatt/PowerShellLoggingModule

Conflicts:
	LogFile.cs