Implementation of notes concept

[moritzhuether]

In order to make it more easy to add notes to you diagram, a new note concept was designed. The following will be implemented:

• A box should be able to contain a string in quotes ( "Text") which displays this text the same way as attributes for in box notes
  • In case note box, as known from UML, is required, a box can in that way be used purely for documentation
• An hashtag can be placed between signature and tag of a box or attribute (#Text). This causes a small chip to be shown on either the box, the attribute or the associaton.