Add/update terminology articles for Fuel processes

Added/updated articles with brief information and links to the Fuel Architecture
in the fuel-dev docs and elsewhere as appropriate:

terminology/allterms -- added links for new articles

- amqp
- astute
- cobbler
- fuel-master-node
- fuel
- haproxy

Change-Id: I3faa8e0eedfb78ba4fb890facb10d845666afae4