show loading icon when buying new items

[rorychatt]

At the moment there is no indication that an item is being bought, it is not instant and there should be some loader present preventing users from spamming buy button

[rorychatt]

• Remove alerts when failed purchases
• Handle loading

[rorychatt]

In our current solutions we get an error message logged into console and there is no UI representation of the error.

We should implement an error message modal component here. See ./error-modal.component.html and it's implemented usage.

Main points:

when buying an item we don't have enough money for, we should not use alert message but use this error modal.
when buying an item if we get any error from backend, we should also display it in that box. Special case is for example for ships, only 1 ship of type is allowed for user (can not have 2 copies of the ship)
DO not allow spamming purchase of items