Armorpaint: Fix file browser and node canvas ui scale

[MiloHX]

Give user option to scale the UI up for HiDPI screen.
I am using a 4K monitor on Ubuntu and I didn't find a way to scale the UI up. I can switch back to Windows 10 and scale the whole thing there, but still, proper HiDPI support will be much appreciated.

/Milo

[luboslenco]

Still a bit awkward but added an option to scale UI at http://armorpaint.org/manual/#toc7.1.

[MiloHX]

Great! I tested and it was already usable! There are something not scaling correctly (x2.5):
Project/Assets Tabs:

Drop down lists:

Import popup window:

Lighting / Brushes / Materials icons are not scaled:

Hopefully once the UI scaling feature is robust, it will be implemented into the UI Canvas editor of Armory too, since I encountered the same problem there.

[luboslenco]

Pushed more scaling fixes, file browser and node canvas also get scaled now.