[4.1] Upgraded line awesome to 1.3.0 and replaced all fa icons with la icons

[tabacitu]

Upgraded Line-Awesome to 1.3.0, which provides syntax compatibility with Font Awesome 5.x

Breaking change. Some icon names have changed.
Took the liberty of replacing all icon syntax throughout Backpack from fa fa-home to la la-home, to prevent clashes when using the bootstrap-iconpicker field type.

One problem remains - inside datatables, the ellipsis and ordering carets still don't work:

[tabacitu]

Needs mentioning in the upgrade guide:

• change path to CSS file in config/base.php file;
• change fa fa-smth to la la-smth;
• check that all icons you were using before in your sidebar_content.blade.php still work, or replace them with icons from their website;