Bugfix/#73 minors/majors

Bug fix

• Fixed re-rendering of the tree panel when drag and drop panels.
• removed using material icons to fontawesome icons set.
• Adressed some FIXME comments.

Summary

Apart from what is mentioned in the main ticket you are going to close with this MR, tell us what you have done to achieve this goal.

Does the result of the MR comply to our "definition of done"?

• Unit tests passed
• Code reviewed
• Acceptance criteria met
• Functional tests passed
• Non-Functional requirements met
• Product Owner accepts the User Story

Related

Closes

Changelog

• I added a statement to the CHANGELOG.

Documentation

• I updated the README (if applicable)
• I provided my functions with appropriate documentation

/cc Mathias Göbel, Frank Schneider, Michelle Weidling