Remove old thumb.png files

[Aaron Wells]

In 15.10 we switched to using fontawesome icons to display the icons for blocktypes. Prior to that, we relied on a file called "thumb.png" under each blocktype's image directory (or under the corresponding directory in the theme).

Through an oversight, we left these images in place in Mahara 15.10. In 15.10.0 they were basically useless. In 15.10.1, after the patch for Bug 1510421, they become potentially useful because we began providing both the FontAwesome icon name *and* the thumb.png path to view/blocktypelist.tpl, so a third-party theme could in theory start using them if they wanted to use all .png files for the block picker rather than CSS icons.

However, since we're no longer using these icons in the core themes, they are likely to fall out of support, so we should probably just delete theme from core.

If we do this:

1. Third-party plugins can still provide a thumb.png file (for backwards-compatibility with older plugins, or for plugins that have no suitable icon in FontAwesome)

2. Third-party theme developers can still provide their own thumb.png files for the core blocktypes if they wish. They'll just need to place them under their own theme directory (i.e. /theme/CUSTOMTHEME/plugintypes/blocktype/clippy/images/thumb.png)

So it won't have any effect on what third-party devs can do. It'll just remove some unused and unmaintained image files from the core Mahara distribution.

[Aaron Wells (u-aaronw)]

Probably shouldn't backport this, because it's sort of a feature change.

For testing, just make sure that the icons for all the core blocktype plugins still display properly in the block picker. (i.e., create a new page, and look through the list of blocks you can add to the page)

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/5895

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/5895
Committed: https://git.mahara.org/mahara/mahara/commit/5577c9290f4115b906e564892fc81935e7ab2444
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 5577c9290f4115b906e564892fc81935e7ab2444
Author: Aaron Wells <email address hidden>
Date: Mon Jan 11 14:07:30 2016 +1300

Remove blocktype thumb.png files (Bug 1532642)

Since we're no longer using theme in any of the core themes.

Note that the code to look for a thumb.png file is still in place,
for backwards-compatibility with older 3rd-party blocktypes.

If you're a third-party theme developer who wants to use PNG files
for the block picker instead of FontAwesome, you'll need to provide
your own thumb.png files for each of the core blocktypes, under
your theme's /theme/THEMENAME/plugintype... directories.

behatnotneeded: Covered by existing tests

Change-Id: I6f0578c8f55c620b7b3df42d8959a6d1ea5ad016