Adds support for displaying inline images within content blocks.

Makes use of `WPImageGetter` to load the images in ImageSpans.
Added image spans directly instead of using Html.fromHtml().

This allows for other block actions like linking to still work. I had to limit the image size to 240dp, otherwise the images would load blank white.
Moved `imageGetter` creation outside of the media loop.
Merge branch 'develop' into issue/1835-notifications-inline-images
Removed unused import.
Matched up span exclusion types.
Add a newline to accommodate additional images in the content.
Remove image alt text when encountered.
Merge branch 'develop' into issue/1835-notifications-inline-images
Add a newline after an ImageSpan is inserted, if needed.

Moved image processing to its own method.
Added a few tests for spannableHasCharacterAtIndex().

Fixed a few imports on existing tests.
Merge pull request #1885 from wordpress-mobile/issue/1835-notifications-inline-images

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