This addresses the problem of
https://nexedijs.erp5.net/#/bug_module/20180719-135FAA8 a KeyError
raised when some categories in a subtree are modified and some are
removed and the corresponding base category is also installed as a base
category.

The problem was that both CategoryTemplateItem, which is in charge of
updating the base category and PathTemplateItem, which is in charge of
updating the categories listed as path both use the same
ObjectTemplateItem.install method, with the same object_to_update dict.
ObjectTemplateItem.install uninstall all objects that are listed in
object_to_update and not in self._objects so something like this
happened when business template from
test_update_business_template_with_category_having_subcategory_tree_modified
is updated:

  1. PathTemplateItem.install is called for the base category,
portal_categories/test_category/modified/removed looks removed, so it is
backed up. Because the the parent paths are not parts of self._objects,
trash tool will create simple trash folder for
portal_categories/test_category/modified

  2. PathTemplateItem.install is called for the paths,
portal_categories/test_category/modified is modified, so the previous
version will be backed up. At this point trash tool looks in the trash
bin and the path for portal_categories/test_category is already present,
so trash tool sees that path exists and does not return subobjects, so
after portal_categories/test_category/modified is modified, the subjects
such as
portal_categories/test_category/modified/container_in_which_child_is_added
are not restored and creating 'added' caused a
KeyError('container_in_which_child_is_added')

The approach is to make CategoryTemplateItem.install only consider base
categories - ie. objects where path is portal_categories/* and not the
subobjects, because they don't belong to CategoryTemplateItem but to
PathTemplateItem.
Co-authored-by: Georgios Dagkakis <georgios.dagkakis@nexedi.com>