Added a lot of stuff, see description

1) Added full navigation between topics and proposals
2) Added complete storing of topics and proposals

Here's the navigation schema:
- from /group, you can create a topic (/new-topic) or see details of a
topic (/view-topic?id=x)
- from /view-topic?id=x, you can create a
proposal(/new-proposal?topic=x) or see details of a proposal
(/view-proposal?id=y)
Dynamic proposal title