Renamed "default-fill" to less misleading "element-type-fill".
Leave "map" etc. working as before for greater compatibility with existing code.
Relaxed constraints on “default-fill:” argument to “limited” for compatibility.
Corrected backward-compatibility note on the default value of the “default-fill:” argument to “limited”.
Added notes about current reference implementation and a possible improvement to it.
Merge pull request #60 from BarAgent/dep-0007

DEP-0007 proposal updates