First draft of DEP-0007.
Addressed line comments.
Updated with feedback from cgay.
Updated "Last Modified"
Changed specification of element-type and default-fill generic functions to take an instance of a collection class, not an instance of a <type>, as their arguments, for DRM compatibility.
It is not actually necessary that all collections support "fill:" and "default-fill"; rather, it is only necessary that any new collections that do use "fill:" use the default fill rather than the first element of a source collection. Also specified that the new generic functions are open.
Merge pull request #58 from BarAgent/dep-0007

Draft of DEP-0007