Programming tools

Look inside ((thx 2 other Snap!-users for ideas!) 

It's a work in progress. Some of the functions it contains:
1. "do": though it may look useless at first sight it’s actually quite handy for a programmer, facilitating code development, debugging and documentation;
2. "let"+ "be": a mechanism for declaring and at the same time initializing (multiple) variables.
3. A logging facility, for debugging and optimization.
4. Commands to modify a variable's value.
5. Advanced sorting options.
6. Memoïzation, both for single~ and multi-variable (recursive) functions.