SQLite branch

This is an initial work on SQLite 3 backend of esoTalk. It works fine on my localhost, but I haven't tested it thoroughly. Please help me developing this branch.

What I did was:
- replacing MySQL texts with SQLite
- removing the host, username and password from the installer
- rebuilding a lot of SQL statements, e.g. changing IF to CASE, GREATEST to MAX, etc.
- removing some unsupported features, e.g. non-unique keys in tables, altering columns, enums, etc.
- changing fulltext search into slower LIKE search

To do:
- test and find bugs
- add indexes
- add fulltext search using FTS3
- modify plugins

Enjoy!