added new sheet_skill
added new exporter to fill sheet_skill(s)
updated copyright header
Merge branch 'develop' into feature/specific-skill-sheet
fixed exception when a PC try to buy a skill from a category he already mastered
fixed skill ordering ( is_school, rank desc, name asc )
changed font on weapon sheet to reflect the other sheets ( Old Style )
fix what git broke....
Merge branch 'feature/specific-skill-sheet' into develop