Using atpackager

This pull request changes the build process to use the extracted atpackager tool.
It upgrades the grunt version used from 0.3 to 0.4.

Before integrating this pull request, the following operations have to be done:
- [ ] integrating ariatemplates/grunt-verifylowercase#2
- [ ] publishing grunt-verifylowercase to npm
- [ ] changing package.json to use the npm version of grunt-verifylowercase
- [ ] integrating ariatemplates/atpackager#1
- [ ] publishing atpackager to npm
- [ ] changing package.json to use the npm version of atpackager