Third BBC-patch

This patch contains

• Bugfixes
• Beautification of code
• Convenience features

Bugfixes

• Adding categories to the component hierarchy now works again properly
• Replaced the deprecated usage of QFileDialog::DirectoriesOnly with the proper way to do it.

Beautifications

• The layout of the component detail view has been improved
  • The layout is more optically pleasing
  • Now also the components name and type are shown
  • The ports now display their tool tips.
• The debug buttons have been removed from the main window and the layout has be reworked accordingly
• Ports in automatically created component symbols now always appear in alphabetical order

Convenience Features

• Attempting to create a new document when there is no active project now displays an error message
• Port descriptors in descriptor files now may ommit port positions.
  • The default (0;0) will be used
  • This is useful when the port position is determined by the symbol generator anyways
• Target formulae now may consist of multiple lines
  • These lines are treated as separate conjugated formulae
• A first draft of saving and loading components in libraries has been added
  • This feature is in an very early stage and will most likely be modified in the future