add copy function to disassembly views

[lievenhey]

This allows the user to copy text from the sourcecodeview and the disassembly view. This is done by reimplementing QTreeView with a custom keyPressEvent function that copies everything from selectionModel() to the clipboard and not just currentIndex like the default implementation does.

[lievenhey]

This makes hotspot behave like the user expects. I would be confused if I select multiple cells and only get the last one into my clipboard.