Class for V3 router packages

The V3 routes were being added by the append_v3_routers function in
each controller package, so the only way state could be stored is in
a global variable which makes unit testing difficult. With this
change, the append_v3_routers functions are put into a class in each
package. This will eventually be used to store JSON Home data.

bp json-home

Change-Id: I744a4c82dc84bb1a8d29d0314e3c51cc43c077a2
Merge "Class for V3 router packages"