bgpd: peer / peer group dampening profiles

Changes implement dampening profiles for peers and peer groups. This is
achieved by introducing the possibility to have multible existing
dampening configurations with their own sets of parameters and lists of
associated paths.

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>
Signed-off-by: David Schweizer <dschweizer@opensourcerouting.org>