implement decryption

adjust command-line to require no file names or exactly two, input and output
remove -G and -R options
specify device with -d option
specify key (in hex) if necessary with -k option
better warnings and errors throughout

enforce device type of mmcblk, fail if /sys/block/<device>/device is not a readable directory

fail if the device isn't an mmcblk device

add warnings if any registers are not properly read

adjust formatting of pastable commands

add README

add shell script to on-device key extraction

output in hex for easier openssl copy and paste

add new source files

add flags for reading and generating key

add header file

add separate path for reading key from SHM

s/getkey/genkey/

generate key from CSD, CID, and SRC registers of SD card

initial commit