JDBC 4.5 support: Firebird-specific implementation of various enquote methods on Connection

[mrotteveel]

JDBC 4.5 adds the following methods to Connection:

• default String enquoteIdentifier(String identifier, Boolean alwaysQuote) throws SQLException
• default String enquoteLiteral(String val) throws SQLException
• default String enquoteNCharLiteral(String val) throws SQLException
• default boolean isSimpleIdentifier(String identifier) throws SQLException

The default implementation is not sufficient for Firebird (especially dialect 1); move the implementation of the equivalent methods from FBStatement to connection, and make statement call the implementation on FBConnection (NOTE: we may also need to move those overridden methods from FBStatement to AbstractStatement for correctness).