Remove all hard-coded terms from e107 and optimize!

Translator's Checklist:

• Remove any HTML from the LAN (bbcodes are okay)
• Use double-quotes. eg. define("LAN_01", "It's all good");
• Make sure "LAN" is used inside the constant name.
• Do not leave empty or unused defines. eg define("LAN_SOMETHING", ""); instead, comment them out with //
• Use $tp->lanVars() for variables conversion. eg. [x] etc.
• Check for duplicate/similar terms (admin only) against lan_admin.php (eg. LAN_UPDATE)
• Check for duplicate/similar terms (frontend or admin) against e107_languages/English/English.php
• Reduce the number of 'defines' as much as possible by using generic terms.
• Do NOT translate debug information. (eg. anything inside addDebug(); or "E107_DEBUG_LEVEL >0" etc. )
• Do NOT translate anything used within e_DEVELOPER.
• If you find a recurring word/term appearing in several areas of e107, please mention it here as a 'generic' candidate in this issue.