Burndown no activity line

Add dummy point with the current time and last value to the data set if
there isn't recent activity, so that flat line is drawn on the graph.
Improve the access controls

The AgileTools user group can be configured via params and if that is
defined, user needs to be in that group to access any of the AgileTools
features.
Use bb_group_params hook to mark used groups
DB schema, init and update functions to separate module
Not safe to use the DB objects in checksetup parts