Add new bcg settings

Hi Brajesh-

I added a couple of settings for BCG and put them all in the same place for ease of use. One is an "enable this plugin" setting that replaces the "disable this plugin" setting. The other is an option for users to change the label "Blog" on the group sub-navigation tab.

The next thing I'm thinking about is making an admin setting so that site owners could choose which categories are available to use. It seems awfully trusting to let your group admins choose from any category. What do you think?

-David