* first steps to metrics

* next small step

* fixed tests

* added comments

* postponed RouterAccepted and RoutesRejected to next step

* read update counters

* added test

* added missing test file

* Route not used any more

* added metrics for session state and time since establish

* increased test coverage, time since establish impl.

* added prom collector

* added metrics endpoint to BGP example

* added metrics for VRF

* removed commented metrics

* fixed logging inconsistency in example

* Update main.go

* gofmt

* fixed typo

* Get rid of holdtimer as a timer

* Fix tests

Package errors provides simple error handling primitives.
Read more on https://github.com/pkg/errors

moved supportsMultiProtocol to FSM because it is internal state of FSM and only used in server package

  The tracked contributing ASNs of a LocRIB will be used in detecting loops
  within AS paths.

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

These will be consumed by a gRPC service. The server has a public
interface that returns basic information, and a snapshotted list of peer
status/info.

Also some small drive-by fixes.