Update documentation

Views:

• filter
• mask
• clip
• zip

Logical operators:

• land -> &&, lor -> ||, lnot -> !

Operators:

• adapt from tutorial/views.html#lazy-images-operators

Misc:

• Reformat Ranges and Neighborhood documentation with a description for each item

• Add a guideline section (top-level) explaining "writing generic algorithm":

  • Explain algo(I&&, O&&) vs. algo(I, O)
  • Explain pros., cons.
  • Explain why we have decided on algo(I, O)