Adding marker, pagination, sort key and sort direction to v2 api

Taking a cue from quantum, use glance's pagination function.

bp api-pagination

Change-Id: Ida7ade8d9332c88679849f7c640651df7e855abb
Add pyflakes

Add tox option to use pyflakes.

Change-Id: Ic77ec3f54cb89341d5b01feb3417e07f43d20c9c
Signed-off-by: Chuck Short <chuck.short@canonical.com>
Merge "Add pyflakes"
Merge "Adding marker, pagination, sort key and sort direction to v2 api"