Add test coverage to confirm that install buttons are disabled or invisible while an installation is in progress

Problem/Motivation

When a project, or set of projects, is being installed, the following things should be true:

• All "Install/Select/Deselect" buttons for individual projects should be disabled.
• The "Clear selection" and "Install selected projects" buttons should not be visible

We need explicit test coverage to confirm that this is the case, and we should also simplify the code that handles this by dispatching events (install-start and install-end) when the install process begins and ends, respectively. The components should listen to those and update their internal state as necessary.