* Replace "template1" with "postgres" database

* add "libpq" to list of common APIs

libpq is probably the most common API for PostgreSQL.

Some minor documentation fixes

[ci skip]

* doc updates for variadic function arguments and type modifiers

* david s requested edits

* updating gppkg reference to no longer mention PL/Java, PL/Perl as separate packages

* pl\python typos; more gppkg cleanup; pgcrypto install

* fixing repeated URL

* Section on xml datatype

* Format corrections

* Fix typos

* Reorganization suggested by Dave

* Format updates

* Update headings

* gpperfmon: update gpperfmon install user docs IPv6

Follow up for commit c52c768e

[ci-skip]

* add info about pl/python multidim array support

* restructure array info so better matches upstream docs

* reorganize a bit, davids other requested edits

* update docs for functions supporting COST and DEFAULT arg clauses

* updates per davids edits

* Relocates gpperfmon reference from GPCC

* Remove emcconnect history and itorators from PDF ditamap

* Remove iterator metrics subtopic from PDF ditamap

* Additional edits to acknowledge gpperfmon without GPCC

* Incorporate gpperfmon.conf reference into gpperfmon_install reference

* #2427: changing the description, default, and set classification of standard_conforming_string to match code)

* small edit

* changing set classification to 'session'

* GPDB DOCS - Add information about pseudo-types.

* update pseudo-type doc based on feedback.

* GPDB DOCS - SELECT( INTO) - add WITH clause (common table expression)

* update SELECT (INTO) docs. Edits and remove RECURSIVE keyword.

* removing/rewording interconnect docs as only UDPIFC is supported in 5.0.0

* update docs to return TCP as valid interconnect for 5.0.0

* removing incorrect warnings stating that GPORCA is not compatible with gpperfmon db

* doc changes to support GPORCA on by default

* gpdeletesystem and pg_dumpall ref page updates

* clarify that --no-gp-syntax removes table distribution clauses

* docs - add plan cache invalidation info

* use correct postgres version, remove reuse statement

* Add RENAME TO option

* Fix typo

* Remove unsupported option

There was a lot of unused code in the gpMgmt bash code that hasn't
been running for quite some time. On top of really dead code, some
codepaths were reachable, but useless (like printing a non-existing
version string). Remove the dead code and replace the version print
with working code which pulls the version from the canonical source.

Mainly fix spacing to avoid rendering the docs as "--option =val"
but also some small superflous whitespace cleanups.

The option description should aptly describe what the option is and
how it's used, a shorter version is not required. Also, the short
version could be mistaken for a parameter to pass in on a quick eye
so remove.

* removing info for older, incompatible netbackup versions

* removing system requirements from backup topic; adding conditionalized reference to release notes for supported netbackup versions