ui: add Traffic Control UI

ui: add Traffic Control UI

adds a list of traffic control rules (with their current usage)
and let the user add/edit/remove them

the edit window currently has a grid for timeframes to add/remove
with input fields for start/endtime and checkboxes for the days

there are still some improvements possible, like having a seperate
grid for networks (the input field is maybe too small), or
optimizing consecutive days to a range (e.g. mon..wed instead of mon,tue,wed)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>