Add nested dict template support; Add x-pattern
For cases where event schema specify `patternProperties` it would be nice
to give that pattern a "human-readable" form rather than a raw regex. This
is now supported by specifying `x-pattern` in the value part of the specified
pattern e.g. `patternProperties:{ "^.*":{ x-pattern: "$THING", ... } }`
Templating had limited record type descriptions limited to value primitives
e.g. `{string: integer}`. It now supports inspecting the values recursively
if the value is `object`.
Updated `m.receipt` to take both these points into account to make it read
better. Tweak receipt module text.
