Possibility to email comments to textual feedback answers

As a course adminisrator/lecturer I spend often time answering to students' feedback. The implemented feature makes it possible to write the replies directy using TMC-server in the following manner:

![feedback_reply](https://f.cloud.github.com/assets/523235/112072/9abec8a8-6b0e-11e2-8fa0-796bbb1b78c0.png)