* change variable 'offline' from global to static
* change variable 'FlushAfterWrite' from global to static
* remove unused global variable 'current_command'
* WaitForResponseTimeoutW(CMD_UNKNOWN, ...) waits for any command
* #include "printf.h" or <stdio.h> in iso15693tools.c to define sprintf()
* and some minor changes/comments
* move communication related code from proxmark3.c and cmdmain.c to new file comms.c
* replace byte_t by uint8_t in uart_posix.c and uart_win32.c
* move OpenProxmark() and CloseProxmark() from flasher.c to flash.c
* move print_lock mutex including initializer to ui.c
* minor changes in printing help texts
* no changes in comms functionality yet
