Load background images from journal

[cvgarciarea]

GCI Task: https://codein.withgoogle.com/dashboard/task-instances/5616648155299840/

I used datastore.find for add images in the view from the journal, and when the user select a journal image, copy that to "/home/user/.sugar/background.[extension]".
Why? Because sugar remove all images journal directory when it's restarted, and aren't yet created when it is necessary to load them as a background, for that, I copy the selected image to the above mentioned address.

[i5o]

Tested and seems good to me; anyone else is welcome to discuss about it

[devAbnull]

sugar3.mime imported but not used.

[devAbnull]

Tested. Looks good :)

[quozl]

Reviewed;

• how is the file eventually deleted; some systems have very little disk space, and every file is important,
• why did you avoid model.py? We have a Model-View design pattern yet your change is to View only,
• in the commit message, please explain what the problem was and how the patch fixes it, (in particular because without a Google account the GCI task link does not work, and besides it won't be useful for future regression analysis; only the commit message is preserved in the git repository, we do not preserve pull request comments),
• in the commit message, please explain how to test the patch; expected result vs previous result,

I'd like to see your commit message grow. Use the first line as summary, then press enter twice before going into detail.

[quozl]

A deleted comment received by e-mail quoted from the GCI task;

Load background from Journal in "Background" section of control panel

Add an option in background control panel section to let the user load a background (image) from journal, showing all images from Journal in the list is another possible way to do it.

Right now the only option is by copying the image to the Documents folder, and then setting it on the control panel.

This is a good basis for writing the commit message, though it would be conventional to describe the problem first, then the solution. See Making commits in the guide to contributing.