Add ability to parse tasks from build script

[gep13]

[gep13]

@devblackops @rkeithhill so I have a VERY basic implementation for parsing the Tasks from a psakefile.ps1 file.

What do you think?

[rkeithhill]

Very cool!

[rkeithhill]

Before you release an update to the extension can I take a whack at a $psake problem matcher?

[gep13]

@rkeithhill no objections from me. We haven't implemented the problem matcher for Cake yet, so happy for you to take a stab at this. :-)

[rkeithhill]

So I've been disappointed to find that invoke-psake doesn't seem to output script name / line number info on errors. :-(

[devblackops]

@rkeithhill psake's formatting of errors can definitely be improved 😄