Testing script

Build script improvement.

+ It understands `-f` command-line option.
+ It runs very quick testing if no file given as argument
+ It sets return code to not-null on test fail.
+ Renamed it from *.sh to *.py

So, there is tests.txt with full test list in repo. For full test we have to run `python 3test.py -f tests.txt`. For quick testing we could run script without any arguments.