+5V to Vcc

Fix for Issue +13 in schematic.
Added fuses

Added two PTC resettable fuses, one to each input terminal. This
resolves issue #3. The extra resistance is a maximum of 50 mOhm per PTC
under normal conditions. This reduces the maximum number of series
panels from 25 to 17 between additional power connectors are needed. The
trip current is 3 A.