Allow question scripts to import files in the same directory

[pauek]

When writing questions about the same subject, it is useful to be able to import a file with common functions, which can be reused for different questions. Right now this does not work by default but can be made to work with:

import sys
sys.path.append('.')

import local_package
...

It would be useful to append the path inside the jutge-make-quiz so that it is not necessary to add the current path of the question file and it works by default.