OpenCards - A free flashcard learning extension for Impress-0.16.2

Bug fix release. New features are:

• Adaptive learning dialog layout depending on height/width-ratio
• Custom field delimiters when importing flashcards (feature request 2054529)
• Bulgarian translation (thx to Stefan Stefanov)
• fixed: Stability problems when switching from one scheduled card-file to the next one
• fixed: session skipping is broken