Make all icons real symbolics

[bertob]

The custom icons for cropping and resizing are a bit off-style and don't recolor:

I'd just use equivalent icons from icon library, specifically crop-symbolic and view-fullscreen-symbolic.

[weclaw1]

Done in 8c075c2fd2c034c079d1ce9a535fef4730cffec1 I have used image-crop-symbolic instead of crop-symbolic because it's a system icon, so I don't have to add it to project.

[nikolowry]

@weclaw1 image-crop-symbolic isn't a pre-installed system icon (on Arch at least). I don't know if you'd like me to open a new issue or not.

Broken symbolic icon:

Working symbolic icon after saving Icon Library's crop icon to ~/.local/share/icons/image-crop-symbolic.svg:

[weclaw1]

Fixed in 610612bd4c8fd34e05eee885e737c0f607265516.