proposal: consistent styling for message action and stream buttons

[niol]

This restyling of the stream buttons and message action button has been working quite well for me.

[jtojnar]

I actually liked the message action button having the same colour as the message bar, even GTK does it.

Either way,

1. The dark turquoise colour is special and should not be overused.
2. The more button is not really important – most of the time scrolling will suffice. The colour should be reserved for important buttons like “log in”.
3. It does not really look well on light backgrounds.

[niol]

Okay for the message action button. Maybe it makes more sense for the stream buttons with auto-stream_more=0 in mobile view.

[jtojnar]

It looks slightly better than the current one:

I still do not like the colour on a light background, maybe something lighter:

Or even more de-saturated:

Either way, localizations should be considered, 150px might be to narrow for many languages.