Group features

Hi, there are some features which could boost the group functionality x-fold. Right now a group is a container for messages sorted forum-style by last comment and equiped with a "send message to all" feature.

The most important function I miss: A different sorting order for posts, especially according to publication date. E.g., in the 红楼梦 group, we follow the novel sequentually and the sequence is important to find old discussions again or to re-start from the top. Now you can still handle it with 20+ posts - but we haven't even finished a quarter of the first chapter. With 200+ or even 2000+ posts sequentially sorting will become a critical success factor.

Furthermore: It would be really cool to have a group-dictionary - which could in the very least be a shared vocab set that can be flexibly expanded and looked up.