Adding a Graph Browser

Graphs are now navigateable under the /graph directory. This is
an initial stab at getting these graphs to be more accessible.
Currently it provides a way for:

 * Users to see what is actually graphable
 * Exposes some of the options available (eg: graph with delta)
 * Exposes the URLs used to access the graphs

This frontend is exposed via the main navbar menu.
Merge branch 'development' of https://github.com/NagiosEnterprises/ncpa into development