Remove normalize constant from metrics module

Now I have also removed the normalize constant and replaced it with the
proper class method in the respective metric classes.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add more code to the license metric

Just started to write some code for the license metric. I will have to
find a good way to consolidate different data licenses and on what terms
it is open/valid and on what terms it is not.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>