Disable tabbing of tree nodes (tabindex=-1).

If Prev/Next navigation is used, then ensure focus is retained after node is loaded and new toolbar is rendered (to retain keyboard context).
Allow plugins to provide Gemfiles
Move plugin gem loading into ASUtils
Add a new script for installing gems for a given plugin
Set plugin gem paths when first initialising gems
Copy plugins to Tomcat when configuring
Incorporate Mark Cooper's New Relic changes as a plugin
[#66125918] minor fix to CSV importer (chokes on BOM)
Introduce an 'add event' toolbar partial and use this on the accession and resource forms
Disable the keydown event handlers in jstree that were overriding basic keyboard actions (for no reason)
Add add event toolbar action to components and digital objects
Only show add event action in toolbar if record is not suppressed