REFACTOR: Rename ParserTests assembly to Pash.System.Management.Tests.

I'm aiming for a 1:1 mapping between code assemblies and test assemblies.
Rename a little more.
REFACTOR: Move `ParserTests` to `Pash.ParserIntrinsics.Tests`

So directory & namespace that matches code under test
TEST: Make it easier to debug unit tests.

With this change, I was able to attach to the nunit.exe process to debug
my tests.
TEST: `Set-Location ; Get-Location`
replace many many usages of 'string path' with 'Path path' in prep for a cleanup on path usages
removed some use of Substring and pushed pathing logic down into the Path object
added a number of tests around the Path object
moved path combination into the path object
tweaked the getDrive code to support 'get-childitem /'
tweaked to support a nested path query
added GetHashCode to the Path. Started adding some file path tests. Added a file path test helper
upated set-location and get-location to work on mac
removing bad comment
fixing a test that broke with variable pathing
added support for navigating up one directory (on the file system)
fixed order of specification helper
couple more test cases around path navigation
removed a bad tests that should be covered by other tests added
two changes

- Initialize filesytem provider's currentlocation with CurrentDirectory
- Throw an exception if trying to CD into a folder that doesn't exist