Added Output Protection board and a number of PSU boards building guides.

Here is the current list of available guides:

VHex+ Classic amplifier
Simpelstark PLUS V1.3 Building Guide
Simpelstark PLUS V1.3 Schematic (high-res)

Tribute-3000 Building Guide
Tribute-3000 schematic and silk screens (high-res)

Amp Control Board V5.3
Amp Control Board V6.03 (isolated grounds for dual mono)
DC Detection Board V4.3
Output Protection Board V1.0

Compact Power Supply V3.1
Dual Board Power Supply V2.0
Modular Power Supply V1.0
NS Series Stereo Input Supply V1.0