Created SD_Card_Layout symbol for creating SD card PCBs.
Created an SD_Card_Layout symbol, which is the old "SD_Card" symbol without the slot related signals. (CARD_DETECT, WRITE_PROTECT and shell pins). This is to enable making PCBs that can fit in an SD Card slot.
The old "SD_Card" symbol was renames "SD_Card_Slot" with a derived "SD_Card" symbol, as not to break designs that are using the "SD_Card" symbol.
Footprint with SD card layout and dimensions is in this PR: kicad-footprints!3193 (merged)