* RIS: Implement cleanup on BMP down event

* Cleanup

Co-authored-by: Maximilian Wilhelm <max@sdn.clinic>

BGP: Fix calculation of maximum BGP update size for non first update

RIS: Implement initial dump signaling in ObserveFIB

Add LPM call to riscli

Fix BMP error logging (add address)

Check if router was removed before trying to reconnect

Add description field to PeerConfig and BGP API

When creating a BGP peer the description field can be filled as well.
This can then be exported via API.

Add functions to AdjRIBIn/AdjRIBOut for RIS

The funtions RegisterWithOptions(), LPPM(), Get() and GetLonger() need
to be exposed by AdjRIBIn/AdjRIBOut. This makes these RIBs usable in
much the same way as LocRIB for the RIS.

Fix crash on route withdrawal with addpath

If addpath is enabled rx then adjRIBIn.RemovePath() will access a member
of p. As p might be nil (e.g. called by fsm_address_family withdraw())
we need to check for this before accessing it.

Allow multiple AFISAFIs in AddPath capability