[FEATURE] build system

new pull request for the old closed pull request #111 

@Schlaefer original commit message:

I put together a simple build system to slim down the repository and ease the release work.

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Adds [phing](http://www.phing.info/) for task management as dev composer requirement. Configuration in `build.xml`. Usage: run `composer install` as usual and call `phing` bash script in root.

Build system:
- adds phing task to create an enduser ready .zip for homepage upload with all necessary vendor packages (specify branch and tag)
- depends on git and composer installed locally
- removes all "lib/vendor" code from repository

phpDoc:
- adds phing task to create phpDoc
- adds phpDoc as dev composer requirement
- removes "docs/" from repository