Collective.iconifiedcategory

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- Fixed code to work with `plone.app.async` as in this case, there is no
`REQUEST`. To do this, needed to get the `images` view by instantiating the
`ImageDataModifiedImageScaling` class, this could be a problem if it is
overrided by a subpackage.
[gbastien]
- Tried to fix again tooltipster popup when categorized element title is
displayed on several lines...
[gbastien]

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- Avoid vertical scroll in tooltipster popup when categorized content title
is displayed on several lines.
[gbastien]
- Force use distribution trusty in Travis.
[gbastien]

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- Overrided `ImageScaling.modified` to take into account real stored icon file
`_p_mtime` instead category `_p_mtime` because the category's `_p_mtime` can
be modified for several reasons and that breaks existing content using the
icon. Moreover, it is now necessary to update elements using a category only
when icon file changed.
[gbastien]
- Force display small icon in select2 droprown so it fits the available space,
this is the case when a large icon was uploaded. Added description on field
`ContentCategory.icon` explaining to use a 16x16 image icon.
[gbastien]

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- Use ram.cache for utils.get_ordered_categories to cache during a REQUEST.
[gbastien]
- Added parameter `only_enabled (True by default)` when
`using utils.get_ordered_categories` and
`IconifiedCategoryGroupAdapter.get_every_categories` to be able to have every
categories in utils.sort_categorized_elements.
[gbastien]
- Use generated url for `scale mini` as icon url so it can be cached.
[gbastien]
- Trigger `CategorizedElementsUpdatedEvent` after elements using a
ContentCategory have been updated.
[gbastien]
- Use `natsorted` instead `realsorted` to sort annexes by title.
[gbastien]
- Updated upgrade step as step to 2100 should be done before step to 2000...
Removed step to 2000 and integrated it into step to 2100 so we first compute
ContentCategory icon listing scale then update every categorized elements.
[gbastien]

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- Display `content_category` title at the top of `categorized-childs-infos`
tooltipster view.
[gbastien]
- Use `natsort.realsorted` to sort categorized elements on their title,
elements are sorted regardless of uppercase or lowercase title.
[gbastien]
- Moved `context._p_changed = True` to the `utils.sort_categorized_elements`
method so we are sure that calling it will correctly manage `_p_changed`.
[gbastien]

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- Adapted CSS regarding `FontAwesome` where font name changed in version 5+
from `FontAwesome` to `Font Awesome 5 Free`.
Require `collective.fontawesome >= 1.1`.
[gbastien]