Improve READMEs + documentation

[tomhea]

flipjump/stl/README.md

• Flipjump tutorial: Give newcomers a clearer understanding of what FlipJump is and why they might want to use the standard library. This will be especially helpful for users who are not familiar with FlipJump. Create a useful program from scratch!
• table of contents
• Add examples of using the standard library. The usage of the stl should be documented much clearer.

README.md

• table of contents

add a programs/README:

• add a short README.md
• add documentation line "// brief.. " for every programs/*.fj file, which explains what's its purpose.

flipjump/*.py

• add a docstring to every python file in the flipjump package, and to every package's init.py too.