Order part1

- Re-arrange guides in sidebar
- Re-structure Order guide topics
- Fix snippet directive to try all langs, even if a snippet for one lang cannot be found
- Explicitly clarify funds may sit in escrow, both marketplace and Order, for a maximum of 30 days.
i think more than one merchant bank account can be credited. but only one _merchant_ can be credited.

e.g.

For each ``Order``, only one merchant and the marketplace may be credited.