[feladat @ 209] Modified some of the INSERT queries to make them compatible with pgSQL

[feladat @ 208] When in the zone listing letters are shown (too many zones to show on a single screen), the start letter is clickable only if there are any zones starting with that letter. If the users asks for a start letter that has no zones (because of bugs like the one fixed in r207 or because user manipulates URL in browser), a PHP error was shown. Code now verifies number of zones now first.

[feladat @ 207] Bugfix. The letters shown just above the list of zones was showing clickable letters, even if there were no zones starting with such a letter.

[feladat @ 206] Added database structure for PostgreSQL and fixed some queries to be compatible with PostgreSQL. Bugfix in delete_supermaster.php

[feladat @ 205] Bugfix. A user with with at least view access could change user details, including the assigned permission template, for which he did have rights. Reported by Maarten te Paske.

[feladat @ 204] Bugfix. Even if one did have the 'add supermasters' right, the menu option wasn't shown. Reported by Maarten te Paske.

[feladat @ 203] Changed field type for password entry field in 'edit user' window from text to password. Now password is no longer shown in plain tekst.

[feladat @ 202] Changed field type for password entry field in 'add user' window from text to password. Now password is no longer shown in plain tekst.

[feladat @ 201] Fixed a typo in the description of 'supermaster_edit' permission.

[feladat @ 200] When loading SQL database structure user 'administrator' has all possible permissions enabled, both ueberuser and others. This may bring confusion, especially those that didn't read the documentation. Now only 'user_is_ueberuser' is enabled, all other disabled. No functional changes. Suggested by Maarten te Paske.