Add support for batch-deleting/batch-selecting bundle items.

[71]

This adds new icon buttons along with "archive all": "delete all" and "select all." In "Options," these buttons can be toggled on and off (the default is to only show the "archive all" button, like now).

Please let me know if you have suggestions. The icons come directly from Material Icons so you may want to modify them. I did not add a custom style for the checkboxes in the options page either.

[teresa-ou]

Thanks so much for working on this! I really like the functionality you've added here.

What do you think about moving the select-all icon to the left and changing it to a checkbox, so that it lines up with the checkbox that's on individual messages? This would allow the user to select either messages in a bundle or individual messages by moving the mouse down in a straight line. I think select-all for the date ranges could stay on the right -- it's a little inconsistent, but I think that would be okay.

I haven't taken a close look at the code yet, but I'll do that this week.

[71]

Thanks for the review, I'll implement everything when I get the time.

[71]

Alright, I added your changes and tried my best to keep the Git history clean (hopefully that did not cause weird things...). I actually made those changes a long time ago so I'm not 100% sure they answer all your requests (but AFAIK they do). Please let me know if there's anything more I should do!