Update ZXCapture.m

Changed from 'assign' to 'strong' to fix problem where we're assigning retained object to unsafe and unretained variable.
Update ZXPDF417HighLevelEncoder.m

fix bug: if continuous digit count is greater than thirteen, encode will failure, result cannot be decode again.
Update ZXAztecWriter.m

fit output image size to input width & height
Separate unit and blackbox tests into different targets

By default both sets of tests will still run, but this makes it easier
to run just one set of tests.
Fixed possible crashes when Modal ViewControler conforms to ZXCaptureDelegate.
Version bump: 2.2.3
Fix project file
Merge commit 'bf2b2d9b3c3d9627ef3f83c8866ae25e99914764'