Documentation and l10n improves

Documentation improves

• Update date and version numbers
• Use suitable tags, add empty lines and re-indent (more readable)
• Suitable capitalization and punctuation
  • Preserve upercase capitalization in the 'Practice Mode' section
• Text added to 'screeninfo' and 'caption' tags (screenshots)
• Add guiicons an use more entities
• GUI sync and shortcut fixes
• Delete a section:
  • Counting an Answer as Right
  • Parley_practice_icon_right.png
  • Parley_practice_icon_wrong.png
• More Screenshots deleted:
  • configure_parley.png Used superfluously to reflect a menu item use "Settings -> Configure Parley..."
  • new_lesson1.png Used superfluously to reflect a context menu use (Add the three ways to do it)

l10n improves

• Add @title:window helpers, capitalization and punctuation fixes
• Fix the menu options in the tips file and delete a tip outdated