(docs) Port recent docs revisions to 1.6.x branch

This commit brings over the relevant changes from commit eb20757, since PuppetDB
1.6 will stay around a while for PE customers. I applied them by hand rather
than cherry-picking, to ensure no 2.1-isms would sneak over.
Merge pull request #1012 from nfagerlund/jul_2014_docs_16x

(docs) Port recent docs revisions to 1.6.x branch
(PDB-769) Deprecate PostgreSQL 9.2 and older

This patch deprecates PostgreSQL 9.2 and older.

Signed-off-by: Ken Barber <ken@bob.sh>
(PDB-834) Update documentation titles for release 2.2

This patch updates all the documentation titles to prepare for release 2.2.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #1056 from kbarber/ticket/master/pdb-769-deprecate-postgresql-93

(PDB-769) Deprecate PostgreSQL 9.2 and older
Merge pull request #1058 from kbarber/ticket/master/pdb-834-update-documentation-headers

(PDB-834) Update documentation titles for release 2.2
Merge branch '1.6.x' into stable

* 1.6.x:
  (docs) Port recent docs revisions to 1.6.x branch

Conflicts:
	documentation/api/query/v1/resources.markdown
	documentation/api/query/v2/fact-names.markdown
	documentation/api/query/v2/facts.markdown
	documentation/api/query/v2/metrics.markdown
	documentation/api/query/v2/nodes.markdown
	documentation/api/query/v2/operators.markdown
	documentation/api/query/v2/query.markdown
	documentation/api/query/v2/resources.markdown
	documentation/api/query/v3/events.markdown
	documentation/api/query/v3/query.markdown
	documentation/api/wire_format/catalog_format_v1.markdown
Merge branch 'stable'

* stable:
  (docs) Port recent docs revisions to 1.6.x branch
(PDB-810) Load test structured facts indices.

This patch addresses some performance issues for structured facts

- deletes the index of fact_values value_integer and value_float.  These
  indices were dead weight since a coalesce causes them to be disregarded.
  This is a stopgap solution to be augmented by PDB-811

- creates a trgm index on fact_values column value_string, so that our trgm
  indexes are now on fact_paths and value_string. This greatly speeds
  up queries on value_string and only moderately affects the table size. See
  https://gist.githubusercontent.com/wkalt/42792c53a5dc9f0840c4/raw/29f261316bc7e39d888250401f0b1f1c8c28a87b/gistfile1.txt
  for some comparisons on a 2000 node dataset with 100 facts per node.

- put a DISTINCT clause in our garbage collection on fact_paths.  This incurs a
  minor performance cost in small datasets, but yields a tremendous benefit in
  large and highly duplicated sets by reducing the load on the accompanying IN.
  (see https://gist.github.com/wkalt/09225b71588c35674827)