decouple CoordSystem2D from Beam, and minor cleanup in related context

See merge request !228

Annotations to GUIDomainSampleVisitor and other copy edits

See merge request !226

Core: minor cleanup in Instrument context

See merge request !227

fill toolbar with actions, not with buttons

Closes #103

See merge request !225

Select items after inserting to sample designer

Closes #7

See merge request !224

Refactor UI creation of SimulationView

See merge request !220

this fixes #103 (GUI: "More..." button in JobWidget is not working)

explanation for changes: filling toolbars with buttons breaks the "more"-button functionality, therefore use the already existing actions to fill the toolbar

this fixes #7 (GUI: After inserting multiple items to the sample editor they should all be selected)

Prepare Beam for refactoring of distribution handling

See merge request !222