chat: resize attachments (images only for now): if attachments to send contain oversized image, a checkbox will be shown (activated by default) to reduce automatically the size. The background color now cover the whole attachments to send widget. If not already specified, media type is guessed from filename when adding an attachment.

f95d0c31d45558c7b3e2fc39398f51eb0190bdca 0.7.0a1
4233be74572a1af8eebd502c009a10641c63ca0c 0.7.0a3
5c28cf8815319abd8c963022091cf4726764a3e6 0.7.0b1
51f73d210da908c9fb292e6bd7fda42a9d2b8453 0.7.0