Of Mice and Passing Arguments to Commands in Powershell v2

Resolves #134 
Replaces #137 

There's an issue with how passing an argument like `-d"ToolsDir=$toolsDir"` in Powershell v2.

Basically, the variables aren't being interpolated as we'd expect.

After trying various workaround, I've thrown in the towel and made a change to rewrite the template instead.

Now doing this:

![](http://cheaperthantherapy.me/wp-content/uploads/2013/03/drinking1.gif)

Oh, and made some changes to the `Get-ProjectItem` method to make it more robust and less procedural.

TODO:
 
 - [x] test that Powershell V3 isn't impacted by these changes
 - [x] kill off the verb warnings in `commands.psm1'