Added generate To File for specified directory.
Added generate To File for specified directory.

Added overloading method generateToFile with File as input parameter and
List of Files as result;
Removed unused import in BaseTypeProvider test and BaseYangTypes;

Changed binding-generator, yang and sal maven pom files to use java 1.7;

Signed-off-by: Lukas Sedlak <fdf21dcad6059db2488908270604c8e78d2e64aa@cisco.com>

opendaylight/yangtools,522986491/yangtools,NovusTheory/yangtools,opendaylight/yangtools