Feature/touchbar enhancement

[gegu]

Added icon to show last arrived image, as suggested in #91 . This icon can have three states:

• Default, nothing new

• One new image

• More than one new images

Please let me know what you think and what can be improved.

[Trenar]

I like it. However, I think a brighter color would be beneficial for elder people.

Another way of indicating multiple images would be a single icon with a small encircled number (as known from Android phones or so)

[sohamakl]

For me it‘s perfect. I don‘t like the little numbers as an overlay of the icon.

[Trenar]

Matter of taste :D I'd be fine with this as well but wanted to mention the other way :)