There is no explicit binary type in Firebird. It can be accomplished
using the CHAR type with a special character set, which tells the
database that it is binary data and there is no collation. (called
OCTETS).

Because of that, we also need the character set to decide the exact
column type.

And also refactor some parts of the driver:
- Create class to determine internal type from firebird type, subtype,
scale and character set.
- Use internal type (DataType::XXX) in XDatabaseMetaData::getTypeInfo()
indirectly. (We want to return a Firebird type for each internal type,
not in the opposite direction.

Change-Id: Ica56a84d89253e11936e7012086fe1d9f61a65f0
Reviewed-on: https://gerrit.libreoffice.org/47091Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tamás Bunth <btomi96@gmail.com>