ADD converter STBInfo - renamed from pliLayoutInfo.py to not conflict on modifications

Usage:
<convert type="STBInfo">{FlashInfo,HddInfo,HddTemp,LoadAvg,MemFree,MemTotal,SwapFree,SwapTotal,UsbInfo},{Short,Full}</convert>

    <widget source="session.CurrentService" render="Label" ...
      <convert type="STBInfo">MemTotal,Short</convert>
    </widget>
    <widget source="session.CurrentService" render="Label" ...
      <convert type="STBInfo">HddInfo,Short</convert>
    </widget>
    <widget source="session.CurrentService" render="Label" ...
      <convert type="STBInfo">UsbInfo,Short</convert>
    </widget>