[BOOTTHUNDER] fix key input to lanch fallback shell
[SHELL] support of multiple stdio
[SHELL] create seperat shell on both uarts
[SHELL] use shell context for script execution
[BOOTTHUNDER] boot from sd1 (ext2)
replace BT_stdsh with properly created shell handle
[SHELL] fix arch_bootm command
[BOOTTHUNDER] fix key input to lanch fallback shell
[SHELL] create seperat shell on both uarts
[BITTHUNDER] Upgraded bitthunder submodule for latest bootthunder code.
[BOOTTHUNDER] Made bootthunder nice and configurable.
[BITTHUNDER] Added BT dependency.