Custon entityreference selection plugin

Implements a CTools plugin for the selection of referencable items
for an entity reference field.  It behaves very similar to the
view-bsaed selection plugin shipped with entityreference, but
allows for configuring a separate view for admin and other users.

Addresses #3484
Rename custom entityreference selection plugin

Use ``adminviews`` instead of ``multiviews`` as it better reflects
the intent of the plugin.

Addresses #3484
Update entityreference view displays to add display for admins

Update the ``my_boards`` view to add an Entity Reference display
that shows all boards.  Update the Board field of the Board Term
content type to use the custom selection plugin and use the new
view to provide the options.

Clone the ``my_boards`` view as ``my_members`` and change its
content type to be "Member".  Use its Entity Reference displays
to select the options for the Member field of Board Term.

Addresses #3484
Merge pull request #12 from ghing/3484-filter_entityreference

Different filters for board term entityreference fields depending on whether your an admin or a clerk user