The names of many variables were too similar. To make the code easier
to follow we renamed:
* _captureElem to _capturedElem
* _captureElemChanged() to _capturedElemChanged()
* captureElem to proxyElem
* elem to target
Co-authored-by: Alex Tanskanen <aleta@cendio.se>
Co-authored-by: Niko Lehto <nikle@cendio.se>