Fix activating power in slot 12 on touch devices

Closes #1211
Combine unlockClick() and click() in MenuPowers
Don't show mouse tooltips when using NO_MOUSE
Always show upgrade buttons for powers that have upgrades

This better exposes which powers have upgrades (and which ones don't).
If the player doesn't meet the requirements to upgrade, the button is
simply disabled.
Allow upgrading powers with keyboard/joypad

Since upgrade buttons aren't in the tablist (and adding/removing them
dynamically would be troublesome), powers can be upgraded by dropping
them immediately after picking them up. This is identical to activating
items in the player's inventory.