Remove various deficiencies of the manual.

Document bind_ipaddr (lp:bug#1032240).
Separate triggers into an own section.
Clarify that the network now is fully asynchronous.
Clarify how atomicity works in stored procedures.
Provide an overview of possible operations in the data model.
Add a stub for system-specific installation notes.
Fix all references to be stable between builds of the
manual, so that an external link to, say, memcached-protocol
stays valid over time.
Merge branch 'stable'