Bug 20650: Switch single-column templates to Bootstrap grid: Various, part 3

Bug 20650: Switch single-column templates to Bootstrap grid: Various, part 3

This patch updates various unrelated templates to use the Bootstrap
grid. In each case, confirm that the indicated page looks correct.

This patch also corrects a couple of capitalization errors and removes
an unused template: virtualshelves/merge.tt.

 - Tools -> Patron card creator -> Manage -> Card batches
   - Export a batch
   - The pages inside the modal window should look correct: Both the "X
     batch(es) to export" screen and the "download exported batch(es)"
     one.

 - Tools -> Patron lists -> Edit list
   - The patron list add/edit form should look correct.

 - Disable plugins in koha-conf.xml.
   - Tools -> Plugins
   - The "Plugins disabled" page should look correct.

 - Enable plugins in koha-conf.xml
   - Tools -> Plugins -> Upload plugins.
     - This page should look correct.

 - Tools
   - The tools home page should show three columns: Patrons and
     Circulation, Catalog, Additional tools.
   - At viewport width below 768 pixels content should reflow into one
     column.

 - virtualshelves/merge.tt has been removed as it is unused. Search the
   codebase for references to it. There should be none.

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>