Source widget polish

[sssoleileraaa]

Description

Towards #332

Move timestamp to "metadata" column below paperclip icon and polish source widget and format it to be 'DD MMM' (day and three-letter month). This also fixes a bug on master where the icon is partially hidden whenever there is a scrollbar in the sourcelist.

When no attachment exists, the timestamp aligns with the preview header (source name), otherwise it aligns with the first line of the preview text.

Note: The paperclip provided in the inventory list needs modification either in Qt (will require some refactoring) or in the SVG file itself (can be done with a transformation function).

[sssoleileraaa]

If you want to test this with a sample preview string, you can use mine, which is already the correct lenght:

self.preview = QLabel('Parsley shallot courgette tatsoi pea sprouts fava bean collard greens dandelion okra wakame tomato. Dandelion cucumber earthnut pea peanut soko zucchini.')

[sssoleileraaa]

For review, compare with zeplin style guide for source widget. Just compare with the min size one since the sourcelist width is fixed for now.

[zenmonkeykstop]

Using the dev SD core environment and running the client from the same dev VM, I'm not seeing any preview text (or the branding image, though not in scope for this PR). Screenshot attached.

Otherwise the source widget matches the description and Zeplin version.

[sssoleileraaa]

Test Plan update:

To see mock preview text you can set self.preview in widgets.py:

self.preview = QLabel('Parsley shallot courgette tatsoi pea sprouts fava bean collard greens dandelion okra wakame tomato. Dandelion cucumber earthnut pea peanut soko zucchini.')

This is for the purpose of making sure it uses the correct font styles etc. for when we actually have the backend functionality to support getting the last activity of a conversation and update an individual source widget in the source list to display it.

misunderstood scope

[zenmonkeykstop]

Source widget displays as described and conforms to Zeplin version. The paperclip is displayed for conversations with downloads, and not otherwise, and the date displays as described.