First Boss added and some gameplay changes

- A new boss enemy added to the game. Every 10th level of a game is a boss level where at least 1 boss comes through the portals.

- Drones have been removed from the game. While they seemed like an interesting new twist in this genre, but they also made the gameplay much slower than intended and their behaviour was not clear, so they made the game more difficult to undertstand for no reason. So, from now on buildings generate resources on their own and those are automatically added to the available resources/products.

- Each map now has a minimum wave count to clear to be considered "completed". When this number is reached, the game automatically turns into endless-mode, so new waves come right after the previous is finished. Game completion is not yet tracked, but the more endless waves are cleared, the more points the player will get.

- Top UI has also been reworked. Minerals, resources and products are separated into their own group and the mouse over tooltip behaviour is also fixed so the description does not disappear and shows up again when the player moves the cursor from the item's image to the item's amount text.