Fix bug of twice the same parent during skill up

Fixed a bug where the display of parents displays twice the same skill
instead of both parents.
Cleaning userprefs fi
reformat (no change)
Pick parents by # of uses instead of random
Generated skills now get sprite from parents

Randomly.
Revert "Generated skills now get sprite from parents"

This reverts commit 86769625de46c0ad0879378fffe2e63c853e1534.
Generated skills now get sprite from parents

randomly
Merge pull request #3 from jdebon/julien_perso

Several improvements; See list of commits