fix usart2: rcc, basic bluetooth modem
u8g_epd_btm: Prints text received over BT modem on EPD.
Basic RTC config.
power saving: WFI in Idle, slow clock. Clock face drawing
stm32f103_rtos_u8g_epd_btm: rtclock, reorganize files
battery voltage measurement
utils
update global BOM
doc/swarch.svg, swtasks.svg