Adds length to String cloumns in datamodel to fit with SQLite requirements.

A limit of 200 characters has been put for each string.
It should be way more than needed (maximum tweet size is 140 characters)
Corrects some unicode problems in datamodel
Adds unicode support in mysql database connexion.
Removes all try/catch in commits that were used to avoid SQLite limitations.

FIXME: There is still some problems with special characters handling in MySQL, but it doesnt cause any problem for the leaderboard printing so far.
It has to be fixed though.

TODO:
Add separate encoding parameters in basic.ini
Separates encoding scheme for database connexion in ini file.