Include reason for replication failure in _replicator doc

closes COUCHDB-1647
Fauxton: Add preview to edit index and fix preview bug
Fauxton: Remove databases from breadcrumbs
Fauxton: hide reduce options for no reduce
taking changes from 1.2 to stop service
Merge branch '1795-fix-pidfile-race'

Patch via Dileep Bapat
https://github.com/dileepbapat/couchdb/commit/f90476074504058c81a6e73814266a5a0724fc55.patch
Docs: fix indention issues.