Add working directory option to Exec function

[DaveSenn]

I think it would be very useful to have an option to set the working directory when executing script blocks (For example if you want to run git in the root of your repository and not in the directory containing the script).
Because of this I added a workingDirectory option to the Exec function.
The option is optional. If specified the current path gets saved using Push-Location and the current location gets set to the specified working directory. After the script block is executed the location will be set back to the previous location.

[rvdginste]

Because I use this pattern a lot in my scripts, I want to suggest to put the "Pop-Location" in a finally block. The end result would then be something like the following:

Push-Location
try
{
  # ....
}
finally
{
  Pop-Location
}

If an exception is thrown in the body of the 'try' clause, then the script will still end up in the location it started from...

[gep13]

@DaveSenn what were your thoughts about the suggestion from @rvdginste? Did you want to incorporate it into your PR? Thanks!

[alexandear]

@DaveSenn up

[DaveSenn]

@gep13 I like the suggestion of rvdginste. It's a good idea to move the Pop-Location statement to a finally block. With my solution, the user could end up in a wrong directory, if some script/exe fails.
Please see #200

[devblackops]

Closing this out as the better solution using the finally block is in PR #200