(#149) Write out all environment variables

- Using the list here:
  http://www.appveyor.com/docs/environment-variables

  Write out all the environment variables from the Build Worker for reference purposes, which can then be inspected and appropriate action taken.
(#149) Removing Environment Variables not required

- Looking at the output, there are some that are of no use right now, so let's not include them.
(#149) Restructure if/elses

- Create structure such that, based on whether on develop/master, with or without pull request, appropriate task is called
- Also, when running locally, just do what is normally done
(#149) All is good, run default PackageSolution Task

- Seems like things are working, so need to test this on actual develop branch as well, with no pull request
(#149) Finalising decisions for Tasks

- Added in new Tasks for deploying to MyGet and Chocolatey
  NOTE:  These still need work, only placeholders
- Added extra calls in build.bat to make decision about what is required.
(#149) Corrected syntax error

Doh!
Merge pull request #150 from gep13/feature/Issue-149

Incorporate AppVeyor Environment Variables into Build Process