OpenDark v1.12

compared to version 1.1 published in June, I've made a few micro-changes :

• technical optimization of the pdf for POD : no transparency, PDF/X-1a format, etc
• font size of footnotes under tables, corrected
• "Craft" and "Concentration" skills put in alphabetical order (rules & character sheet)
• date now in the only order : "The [Nth] of []" similar in British and American English
• clearer sentence at the beginning of the OGL chapter : " Except for the text of the Open Gaming License itself, all this document is designated Open Contentunder the terms of the Open Gaming License. "