Install button label fix for a better understanding

[teo2peer]

Changed label "Shopping cart" to "Manage selected packages" and the icon "fa-shopping-cart" to "fa-cube". Changed checout label from "Checkout" to "Apply changes".

[Bee-Mar]

@teo2peer the reasoning is understandable, and I am willing to change it, but would prefer keep the label to two words like "Manage Packages" and keep the button label to a single word like "Apply". Also, all of the shopping-cart component names should be renamed to be more consistent