Configurability

I added a project based configuration: for each project is configurable each available filter on email content.
This drastically changes the behaviour of the plugin which was previously only partially configurable system wide.
![configurable_content_filter](https://f.cloud.github.com/assets/440593/349359/88b3f41e-9fbe-11e2-91cb-79fe02af76b6.jpg)