Marlin / Repetier, If the printer says we are printing from sd , we are printing from sd
Add isSdSupported() to plugins returns true if plugin supports Sd Cards
check for sdsupport for opperations
AtCore: Ignore the sd print option of AtCore::print if the loaded plugin lacks sd support
Test Client : Toggle sd widget's visibility based on firmwares support for sd cards.
Signed-off-by: Chris Rizzitello <email@example.com>