Add drag-and-drop new entry stubs for OSX.
Remove prior osx-specific drag-and-drop. Added ebib-add-entry-stub to programmatically add entries to the db. Modified ebib-add-entry to use that function.
Adds ebib-add-file-entry to add entry stubs for a file or directory of files. Can use with minibuffer prompt, or easy hook up for drag-and-drop.
Add allow-duplicates-p flag to ebib-add-file-entry. By default, the function ignores adding files already in the db connected with another entry.
Merge branch 'feature-drag-and-drop-file-entry' of git://github.com/lamberta/ebib into lamberta

Conflicts:
	ebib.el
Autogenerate keys in the form <new-key%d>.
Add entry key to ebib-cur-keys-list in ebib-add-entry-stub.
Add / after filename prompt in ebib-add-file-entry.
Some small style changes.