noticing broken items, even when they are not touched. Also coloring
their parents in an orange color, so that the error is noticable even
when not expanded.

For better generality (and was useful for error reporting): All widgets
introduced inherit from a common base class: CustomWidget. It holds a
signal definition that can be used to directly forward signals to its
QTreeWidgetItem underneath.

Fix/robot state memory memory leak

See merge request !319

no idea why it works...

- move into own sub-folder widgets
- Wrapper around QComboBox
- extract ColorPalette creation
- extract string creation for Lists

Fix: Robot State Memory: memory leak

See merge request !318

of git.h2t.iar.kit.edu:sw/armarx/robot-api into feature/skills-manager-edit-arguments

Laser scans memory: Synchronize robot in regular intervals

See merge request !316

Fix/read variable size matrices and optionals

See merge request !315

Merge branch 'fix/read-variable-size-matrices-and-optionals' of git.h2t.iar.kit.edu:sw/armarx/robot-api into fix/read-variable-size-matrices-and-optionals

- add QuaternionWidget
- remove old modal code
- remove Copy and clone of AronTreeWidgetItem
- add recognition of duplicate dict keys
- add countermeasure to tabbing into unchangeable key fields
- make aronType const in AronTreeWidget
- flag tuple code as untested, since aron is currently broken there
- fix weird std::locals setting in AronTreeWidgetSetter.cpp, which causes floating numbers to print as 12,345 with std::to_string()
- add usage of std::launder to make reinterpret_cast more save within the usage of NDArray