also get rid of some TODOs

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