Added function renameColumn in CFirebirdSchema;
Added function dropColumn in CFirebirdSchema;
CFirebirdConnection wrong driver name fixed
README.md double connection string removed
Added function alterColumn in CFirebirdSchema;
Merge pull request #6 from edgardmessias/migration

Added support for migration: renameColumn, dropColumn and alterColumn
Merge pull request #5 from mr-rfh/master

CFirebirdConnection and README.md fixed
Updated version and "thanks" section in README.md