shorten constant name
shorten CONFIG to CFG
shorten MININUM to MIN and MAXIMUM to MAX
improve readability in 'base' modules
done improvement in for 'refdb'
done improvement in for 'preproc'
done improvement in for 'engine'
done improvement in readablity for 'app' level
reimprove readability in 'config' module
another reimprove 'config' module
Merge branch 'feature_improve_code_readability' into development