cosmetic
relative path program location fix
healthcheck: add possibility to check labels to select loopback IP

This allows one to use several instances of the healthchecker, each
instance handling a subset of the loopback IP. This is compatible only
with Linux currently. The documentation at the top has been updated for
that.
Merge pull request #185 from vincentbernat/feature/healthcheck-use-labels

healthcheck: add possibility to check labels to select loopback IP
do not use MED when indexing routes
Merge branch 'master' of github.com:Exa-Networks/exabgp
functionaly undo last patch
healthcheck: don't advertise med when withdrawing a route

There is no MED in a withdraw message. While exabgp doesn't have a
problem with that, it seems cleaner to not advertise one while this is
just ignored.

Closes: #184
Merge pull request #186 from vincentbernat/fix/healthcheck-no-med-on-withdraw

healthcheck: don't advertise med when withdrawing a route
healthcheck: don't advertise community either when withdrawing a route

Only the prefix is advertised in a withdraw message. While exabgp
doesn't have a problem with getting more stuff, it seems cleaner to not
advertise anything else while this is just ignored.

Closes: #184
steal preexec_fn trick from exabgp processes.py, fixes #183
do not force a next-hop to withdraw
Merge pull request #188 from PowerDNS/healthcheckpgrp

steal preexec_fn trick from exabgp processes.py, fixes #183
Merge pull request #187 from vincentbernat/fix/healthcheck-no-community-on-withdraw

healthcheck: don't advertise community either when withdrawing a route
allow recording on ibgp test tool
fix python2.6 compatibility undoing a suggestion from pycharm
fix MD5 for IPv6
Merge branch 'master' of github.com:Exa-Networks/exabgp into configuration