Increase icons set

[ywarnier]

This is a very long-breath task.
In Chamilo 2 (and probably later versions), we will be using Material Design Icons, an open library which generates a sprite which can then be used and colorized in Chamilo.

However, MDI has one big limitations for us: there is not clear definition (that I could find) of a certain number of icons "variations". For example, if you have a "book" icon, you might have a "book-plus" icon with the same icon and a "+" sign, but not necessarily a "book-minus" icon (to remove an element from a list) and a "book-trash" icon (to delete the element). There are many more examples of that.

This leads to the fact that we are missing icons we need, and to some inconsistencies in the interface (you have an icon to delete a document, but no icon to delete a test, for example).

One work is to complement the icon set with the icons we need for visual consistency, but it is important that these icon go through the process of inclusion inside MDI so we don't have to develop a permanent fork of the MDI project (which would require more maintenance over time).

The second work would be to work with the MDI team to define new official ways for people to add "standard variations". For example:

• star (to create a new item)
• plus (to add the item somewhere)
• minus (to remove from somewhere)
• trash (to put in the temporary deletion bin)
• cross (for delete)
• up arrow (to upload)
• down arrow (to download)
• left/right arrows (to move)
• eye open/closed (to hide/show) (although for this we can just use the eye icon on its own)
• cog (to configure)

This is just a quick list.
Obviously, the argument might be that we should just use the "plus", "minus", etc icons for whatever we want to add, remove, etc. But in practice, many interfaces offer the possibility to manage different types of objects, and it's important to have a clear visual sign of what you are adding/removing.

For example, the documents tool has many options (creating documents, folders, uploading documents, deleting documents, converting them to templates, editing images, downloading a zip, etc). That kind of interface requires fine-grained icons and we don't have a clear process to design them and compile them into a sprite in a temporary fork.

The whole process, ideally, should work with only Open Source tools. From what I could read, the MDI team works with licensed non-open tools under Windows. This is an issue for Chamilo developers.