Add a rewards system to BPBible

[GoogleCodeExporter]

There is much extant research suggesting that rewarding people for good 
behaviour or even just unusual behaviour can increase engagement.  We should 
consider such a rewards system for BPBible.  Rewards could be for things like:
* Making ten notes on different verses.
* Using the search a number of times.
* Using particular search functionalities (e.g. searching for a phrase, 
searching for A | B, etc.)
* ...

It should also keep good track of what rewards you have got and what rewards 
are available to get.

For a good example of what you can do with rewards, see StackOverflow.

Original issue reported on code.google.com by [email protected] on 22 Feb 2012 at 12:51