WIP: Just Another expressioN system

This replaces genericExpressions by introducing a similar approach, but instead of using macro and boost magic it uses a python script to fill a Jinja2 template. Documentation can be found in src/lib/access/expressions/expressionGeneration/README.md and the attached image illustrates the structure of this system.

![bildschirmfoto 2014-03-06 um 19 58 28](https://f.cloud.github.com/assets/1655756/2349196/60d2f34c-a561-11e3-9029-2a7524ad7626.png)