Very stable pre-release

This version contains a lot of cosmetic changes and safety fixes. See this commit for changes, but mainly:

• added more blank lines
• every text line has at least 1 space margin from left border
• files' integrity is tested more often
• more exceptions are handled properly

Also changed .exe icon and compiled file is now compressed with UPX. Free to use software based on same license as Python Password. So executable has now 8 MB instead of 10 MB.