Rewritten font support:
* Font support is now Unicode based and TeX font support is dropped.
* cmex TeX font is still used for big brackets.
* The rest of BaKoMa fonts are no more packaged with KFormula. Arev fonts are
packaged instead.
* Unicode table has been separated into different set of tables to
allow symbol selection separation in the future.
* All the symbols in tables are supported in Arev font. If the font selected
by the user doesn't contain the symbol, Arev font will be instead.