Refactor parsers - Githubissues

Re-work of #164 on to the 3.0 branch.

What this PR does:

Removes the dependency on PathTranslationParser from all the Deploy Strategies
Change PathTranslationParser to a simple decorator of original strategy
Move Parsers to there own namespace
Add tests for PackageXmlParser and fix some bugs with not imported exceptions
Remove some redundant code in the strategies to make them a little simpler
Abstract the Parser choosing to a Factory class
Add some test assets for parsers
Simplify unit-tests, especially the PathTranslationParser ones

magento-hackathon / magento-composer-installer