Ignore the "vendor" folder.

Signed-off-by: Marios Sotiropoulos <mai1211@uom.edu.gr>
Ignore cache files.

Signed-off-by: Marios Sotiropoulos <mai1211@uom.edu.gr>
Configure the Doctrine parameters.

Signed-off-by: Marios Sotiropoulos <mai1211@uom.edu.gr>
Ignore irrelevant Symfony-related files.

Signed-off-by: Marios Sotiropoulos <mai1211@uom.edu.gr>