Fix 'foo all catalogs' via the web interface

Evidently Catalog::get_catalog_ids() wasn't quite as unused as I thought
it was.

Fixes GH #18
Clean up the install code a bit

Remove lang/charset copypasta, unnecessary setting of $prefix,
unnecessary constants.
More cleanup of install, add DB port option
Add a working check for database existence

Fixes GH #21
Increase the field size in the ACL entry form

It wasn't large enough to enter IPv6 addresses.
Fixes GH #24
Make Catalog::count_songs use the correct variable

Fixes GH#23