Consistency of encoding / associatedMedia

Use the same definition for encoding and associatedMedia,
as they are synonyms for one another. Also make the definition
agree grammatically with singular vs plural.

Also refer to "CreativeWork" in the description rather than
"creative work", as the former seems to be the predominant form used
for properties on CreativeWork.

Signed-off-by: Dan Scott <dan@coffeecode.net>
First cut at schema for ItemList / ListItem, based on Martin Hepp's draft.
Adding numberOfElements property, as suggested by Alexander Shubin.
Adding example for ItemList from Alexander Shubin,
http://lists.w3.org/Archives/Public/public-vocabs/2014Jun/0122.html
Fixes to JSON-LD ItemList example.
An ItemList example was tagged to show in the ListItem page.
Merge branch 'master' into sdo-itemlist

Conflicts:
	app.yaml
Merge branch 'master' into sdo-itemlist
Merge branch 'master' into sdo-itemlist
Merge branch 'master' into sdo-itemlist
sdo-itemlist.appspot.com
Merge branch 'master' into sdo-itemlist
Merge branch 'master' into sdo-itemlist
Merge branch 'master' into sdo-itemlist
Moved sdo-itemlist examples to own file, conflict avoidance.
Moved ItemList proposal to separate file.
Moved itemListElement into separate file.
itemListElement extracted.
base href now permits https, to avoid browser errors.
Removed <base href...