Implement bootloader #137 (#142)

* Boot: switch to DFU routines. Implements #132 part 1 of 2.

* Boot: boot to DFU shortcut, hard reset USB on each boot. Implements #132 part 2 of 2.

* Deploy scripts: fix path for deploy dfu.

* Bootloader: initial version. Target_f2: rebase, update deployment scripts.

* Bootloader: cleanup, refactor switch2 proc. Readme,wiki: document bootloader.

* Wiki: deploy symlinks as files, bootloader info.

* Target_f2: valid flash size in linker script.

* Github CI: bootloader build and artifacts.

* Bootloader: rename platforms to targets.

* Bootloader: change dfu/os colors.

* disable set -e

* lint code

* add bootloader testing page

Co-authored-by: Aleksandr Kutuzov <aku@plooks.com>
Co-authored-by: aanper <mail@s3f.ru>

target_f2/STM32L476RGTx_FLASH.ld

@@ -63,7 +63,7 @@ MEMORY
 {
 RAM (xrw)      : ORIGIN = 0x20000000, LENGTH = 96K
 RAM2 (xrw)      : ORIGIN = 0x10000000, LENGTH = 32K
-FLASH (rx)      : ORIGIN = 0x8000000, LENGTH = 1024K
+FLASH (rx)      : ORIGIN = 0x08008000, LENGTH = 992K
 }
 
 /* Define output sections */