ISIS-769: precommit and commit

1. First the precommit commits any outstanding updates for configured applib services.
2. Then the JDO commit is performed.
3. Then the IsisTransaction state is set to committed.

Previously the order was 1, 3, 2.  Any exception in the JDO commit would then cause things to get out of whack; see http://isis.markmail.org/thread/anln67ohbvkx4r4s .
ISIS-778: removed EntityLinkSelect2PanelFactory

... because only ever used by ReferencePanel.  Instead instantiate panel directly.

(On way towards combining these two components).
ISIS-778: moved CSS from EntityLinkSelect2Panel to ReferencePanel
ISIS-778: reference panel simplification

... compact component uses EntityLinkSimplePanel rather than EntityLinkSelect2Panel (since simply need to render a link).
ISIS-778: moved html from EntityLinkSelect2Panel...

... into ReferencePanel.
ISIS-778: moving functionality into ReferencePanel

... from EntityLinkSelect2Panel.
ISIS-778: moving further functionality ...

from EntityLinkSelect2Panel into ReferencePanel

In addition, removing org.apache.isis.viewer.wicket.ui.components.actions.ActionInvokeHandler since does not seem to be used
ISIS-778: more stuff moved over

from EntityLinkSelect2Panel to ReferencePanel.  Specifically, the entityIconAndTitle link is now parented by ReferencePanel.
ISIS-778: tidy-up of ReferencePanel
ISIS-778: select2Field moved from EntityLinkSelect2Panel...

... to ReferencePanel
ISIS-778: further clean-up.

Although EntityLinkSelect2Panel has not quite been eliminated, reckon this is in a good-enough state to start on the @BulkParam functionality.
ISIS-778: removing ToDoItem#foo and #bar

... accidentally committed.