limitRecent is confusing

[mpickering]

I assumed that the limitRecent option in settings.yaml referred to how many commits were shown on the graph. However, it doesn't affect that at all and it just limits the number of commits shown on the homepage.

To modify the total number of commits shown on the graph you have to edit the constant cGRAPH_HISTORY in Shake.hs. It would be good to be able to control this from the config file as well.