pep8 fixes
replace double quotes by single quotes
cleanup infinite calls _connection_defaults()
use db setting/variable as was said in documentation
fix pep8
fix version(): `psql --version` return client version, but we need server version
* fix db_list(): instead plain list with dbs properties return well formed dict
* fix docstring in _connection_defaults()
* fix _psql_cmd(): search psql by salt.utils.which
cleanup db_exists()
cleanup db_create(): we no need to check psql, which provide excellent diagnostic messages and return codes.
cleanup db_remove(): we no need to check psql, which provide excellent diagnostic messages and return codes.
fix user_list():
  * multiline query was cause shell error
  * parsing code wait for 13 cells in SELECT result, but query return 12 cells
  * query was not work with pgsql prior 9.1
replace internals user_exists() by call user_list()
pep8 fix
pep8 fix
pep8 fix
get server version by sql query
fix version() usage
* get rid of check_or_die() which is depricated
* use proper import
Updated limit to be escaped like before and after.
Import install command from setuptools if we use them.

This commit fixes bug with option --single-version-externally-managed.
Merge branch 'pgsql' into develop

Conflicts:
	salt/modules/postgres.py