add fill, fillColor, and fillOpacity for rectangles and polygons
typo
since the units are metres, we'd better make the circles bigger
use is.finite() instead of !is.na() to protect against Inf/-Inf values in lat/lng
wip
Revert "wip"

This reverts commit 92219f89b5fa2d630e2fbab0b97df8762361b59c.
Introduce resolveFormula and derivePoints

Also export pointsData generics, this is for testing
Layer-specific data overrides; infer lat/lng

- Add data parameter to most layer functions
- Reverse order of lat/lng to lng/lat in most functions
- If lng and/or lat are NULL, infer spatial points from data if possible
- Change how data is stored; map$x$data means the data will be serialized
  and sent to the client, that's bad
- Add normalize.R examples, we can delete once this all shakes out