support of horizontal trapeze correction added

See merge request !3

The horizontal isosceles trapeze perspective correction is supported
since color-pipe library version 1.1.0. The horizontal correction weight
can be set at the frontend and is forwarded to the color-pipe library.

When installing OpenCV manually, the headers go to directory
/usr/local/include/opencv4. This directory is added to the include search path.

This happens in following two cases:
1. camera is disconnected or
2. application is exited
while recording.

Replaced the "Ok" with "Yes" and the "Cancel" with "No". Reason:
The onAccepted signal is emitted twice when running on Windows 10.

Reasons:
1) not needed and according to Qt documentation
2) causes a segfault

If deleteLater() is called the memcheck complains
about memory leak.

from delete to deleteLater.

Plus, changed the message dialog modality.

Changing the implementation of firmware update:
Stopping camera thread before doing the update
and starting it again after the update completion.

Not tested yet on Windows nor openSUSE Leap 42.
Also, created enum for button ids in types.hpp.

like it was until 2 commits ago. Otherwise, because it is
a double, it never becomes exactly 1 (in autoscale mode),
which causes problem in zooming() function in imgproworkers.

The zooming has to be adjusted still. Factor
should be an integer.

Closes #1

Also,
- corrected typos
- added note next to operation mode choice