[*] report JSON parsing errors and other C++ exception instead of cra…

…shing

[*] fix non-working Python OpenCV module on Ubuntu Linux

at least with version 20.04

[*] add buffer size validation

[*] make application source code relocatable

[*] small cleanup of .gitignore file

[*] fix typo in OpenCV install script

[*] document minimal required OpenCV version

[*] update to MRTech IFF SDK version 1.2