Updated application action icons for icons used in Google Material Design

[Gaboso]

Updated application action icons for icons used in Google Material Design;
Reduced size of icone files

[metaprime]

What's the license on these assets?

[Gaboso]

The icons are available under the Apache License Version 2.0. We'd love attribution in your app's "about" screen, but it's not required. The only thing we ask is that you not re-sell these icons.

Google in https://material.io/icons/

[metaprime]

Thanks! The new icons look good. Additionally, it looks like most of them are a fair bit smaller than the old ones, which will decrease the binary distribution size (always a nice size effect).

I'll double check on the licenses and see about adding notices in the repo documentation and in the app itself.