added saveStyle capability - Developed for ARPA Piemonte (Dipartimento Tematico Geologia e Dissesto)

changed to use QgsSqliteHandle and added QMessageBox include

reread value from style db managing utf8 decoding

formatted with astyle.sh
Merge pull request #1221 from luipir/spatialite-savestyle

added saveStyle capability to Spatialite Provider - Developed for ARPA Piemonte (Dipartimento Tematico Geologia e Dissesto)