Disabled save-button is styled.
Save-btn is enabled and disabled when a relevant event happens.
Merge branch 'save-btn-enable-disable' into rebuild-profile-management

The save-button works based on the presence of the class "disabled-btn" on it.
When disabled, it can be clicked (i.e. not literally disabled), but the click event
has no effect. On the other hand, hovering over it does display the related tooltip.

The button is disabled when a profile is successfully loaded or saved.
It is enabled again when a playlist is renamed, or when a playlist record is
added, removed or sorted.