Treating TIFF and BMP as images cause us to add them to IMG tags, this is very inconsistent across browsers.
You can still upload these files they will simply not be displayed in IMG tags.
Fixes composer warnings when: a) mentioning groups ("By mentioning @group, you are about to notify x people...") and b) mentioning users in a PM ("You mentioned @user but they won`t be notified...")
Ember3 is more picky about having a container being destroyed and it's easier to cause exceptions, especially in tests.
This fix has been initially created for an exception occuring in tests when running discourse-code-review and discourse-polls tests at the same time. `getCurrentUser` method body was failing as the container was destroyed.
Original stacktrace:
```
"Error: Assertion Failed: expected container not to be destroyed
at new EmberError (ember:2929:31)
at assert (ember:1793:23)
at Container.lookup (ember:17736:64)
at PluginApi.getCurrentUser (discourse/lib/plugin-api:56:31)
at allowUser (javascripts/discourse/initializers/init-code-review:38:29)
at eval (javascripts/discourse/initializers/init-code-review:78:11)
at eval (select-kit/mixins/plugin-api:86:19)
at Array.forEach (<anonymous>)
at eval (select-kit/mixins/plugin-api:85:44)
at Array.forEach (<anonymous>)"
```
Somehow a plugin or some new Chrome bug is causing its heuristic to detect
our textarea for the composer as a target for address autocomplete
This is likely a chrome bug but this change is very safe regardless.
New `about.json` fields (all optional):
- `authors`: An arbitrary string describing the theme authors
- `theme_version`: An arbitrary string describing the theme version
- `minimum_discourse_version`: Theme will be auto-disabled for lower versions. Must be a valid version descriptor.
- `maximum_discourse_version`: Theme will be auto-disabled for lower versions. Must be a valid version descriptor.
A localized description for a theme can be provided in the language files under the `theme_metadata.description` key
The admin UI has been re-arranged to display this new information, and give more prominence to the remote theme options.
