Discard changes in the Web IDE

In the Web IDE changes can be made, but there is no easy way to discard them. Currently all changes are immediately staged. We should add a 'Discard changes' button beside the file.

Design

On hover:

• row is highlighted
• icon visible

on hover over icon:

• colored red, as it is a destructive action

First time deleting in current context results in a modal to make sure the user understands its removing all changes on current file.