Bug 16369 - Clean up and improve plugins template

Bug 16369 - Clean up and improve plugins template

This patch makes multiple changes to the plugins home page template to
bring it up to date with current interface patterns.

Test the following changes:

- Breacrumb links have been corrected to include "Tools" in the path.
  Verify that this link is correct.
- A toolbar has been added for an "Upload plugin" button. Uploading is
  an action, not a view, so it should be displayed in a toolbar. Verify
  that the button works correctly.
- Messages are now formatted as messages rather than as headings. To
  test, trigger a message by, for instance, uninstalling all plugins or
  passing an invalid "method" parameter with the URL.
- Incorrect capitalization corrected.
- Plugin actions are moved to a single "Actions" dropdown menu. This
  includes 'Run report,' 'Run tool,' 'Configure,' and 'Uninstall.' Test
  that all these menu options work correctly.
- The standard "Tools" sidebar menu has been added.
- An "onclick" attribute has been removed in favor of defining the event
  in JavaScript. Test by choosing the 'Uninstall' menu item for a
  plugin. Test both confirm and cancel actions.

Also changed:

- Corrected capitalization on the tools home page.
- Adding missing plugins link to the tools sidebar menu.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>