[feature] experimental Firebird DB support

# Firebird support

Adding support for the Firebird database. For now, only two changes were made to medoo.php:

* The data source name format for Firebird was added. Similarly to SQLite, Firebird requires the ```database_file``` string.
* Before running a query, double-quotes are removed. This is because Medoo by default adds double-quotes around column and table names, but Firebird doesn't support that. The solution is dirty and I'll think of a better way of doing that. Originally I wanted to wrap around the ```column_quote``` function, but that gave me a segmentation fault in Apache that I couldn't trace.

**Attention**
While testing, I came across  a bug in the PDO Firebird driver that resulted in the first row of the results always being null. Information about that bug can be found [here](https://bugs.php.net/bug.php?id=35386). The solution in the second-to-last comment on that bug request worked for me, so go ahead and re-build that driver!

Cheers,
Renan