Add upgrades for remaining auto-pickers

Addresses #24.
All auto-pickers can now be upgraded.
Change cursor css for mushroom counter

The cursor is now always the default one on the mushroom counter
Fix load function

The load function now loads upgrades and mushrooms picked properly
Fix berserker upgrade text

Addresses #24.
The berserker upgrade is now properly named.
Change upgrade price increase rate

Addresses #24.
Upgrade prices are now doubled on purchase.