Avoid specific version mention for database extensions

Avoid specific version mention for database extensions

As tsbere pointed out, the 9.1 database script will be used for every
version after 9.1... which makes it confusing to have a version number.
As the primary reason for the difference is the switch to extensions
instead of contrib modules, use a name that flags that difference.

Convert the 9.1 full-text search configuration into a symbolic link
instead of maintaining a separate copy of the file.

Given that the pre-9.1 database script was focused on the creation of
PostgreSQL contribs, call it that, rather than the (now confusingly)
generic "create_database.sql" that existed from a time when contribs
ruled the earth and extensions were mere fantasy.

Adjust eg_db_config.sql for these changes as well - including the
command line switches.

Signed-off-by: Dan Scott <dscott@laurentian.ca>