Refactor the crop js component and the view spaces/edit, refs #412

Trying to make the crop js less dependent on the tags used in the application
and more contained (all jquery selectors are searched on a restricted scoped, for
example).

Includes several other small related changes: using more data attributes instead
of tags to pass information to the js, reorganizing locale strings, use less
ids and more classes, and others.
Hide rails footnotes in crop forms, refs #412
Replace more icons images with font-awesome, refs #967
Prevent broken images from breaking the layout too much

Happens in firefox because the image is replaced by the alternative text and
it doesn't respect the width and height set to the image.
Fix missing locales for simple_form
Finalizing the view space/create, refs #456

Added a sidebar with examples of a few spaces already created, makes the page
less 'empty'.

Also includes some refactoring and cleanup in space's controller and model,
and more tests for both.
Fix cut tooltips when inside elements with overflow:hidden

Tooltips are now appended to the <body> that, so doesn't matter how the tooltip's
parent css is defined, it should always work.
Also tooltips don't need a min-width anymore.
Add css mixin to deal with broken images, complements 9f932629790

Almost the same that was done before, but now everything is done by a mixin.
It was also improved a bit.
Improvements in LogoImagesHelper

Was including the url attribute in <img>, but shouldn't.
Nothing else changed in the functioning, only refactored a bit and added pending
tests.
A lot of improvements in events, specially for views, refs #383

Made the views we use look better, and at the same time refactored and removed
*a lot* of things related to them. Few changes in controllers/models, most
where in the views and related assets.
There's still a lot to be improved, specially in the controller.
Cleanup and improvements in events, mostly for the controller, refs #383

Cleaned up the controller a lot and added tests (most pending).
Includes some changes in the views too, complements 18091c76cdb.
Inform if the space is public/private in the page titles of spaces

There was no information in the pages of a space showing whether it is public
or private.
And allow titles of spaces to use more space in the page header.
Inform the current timezone when creating/editing an event
Add the author of an event as an organizer by default, refs #383

Also cleaned up the Event model a bit, but it still has a lot of things that
can be removed.
Show more information in events/show, refs #383

Show the date the event ends and make it look better when some of the attributes
of the event are not set.
Add options to toggle repository and remove the space in spaces/edit
Better definitions of what is mandatory in setup_conf.yml, refs #781

Several things are actually mandatory, if they are not in setup_conf.yml the
application will crash in some places. More information about it will be added
in the docs.
Add a button to end the meeting in spaces, refs #866

Added the button for spaces and also improved a bit the view for user rooms.
Merge branch 'rnp-institution' of github.com:mconf/mconf-web into rnp-institution
Tests for institution and new methods