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>

wiki/Testing.md

@@ -0,0 +1,37 @@
+# Bootloader test
+
+1. # Clean flash
+2. `make -C bootloader flash` # Load bootloader
+3.  # reboot device
+    1. Press right
+    2. Press left
+    3. Wait 0.1 s
+    4. Release left
+    5. Release right
+4. Wait 0.5 s
+5. # Expect no FW
+    1. Expect: no uart welcome message
+    2. Expect: red led on
+    3. Expect: no USB
+6. # reboot device and go to DFU
+    1. Press left 
+    2. Press right
+    3. Wait 0.1 s
+    4. Release left
+    5. Wait 0.5 s 
+    6. Release right
+7. Wait 0.5 s
+8. # Expect DFU
+    1. Expect: blue led on
+    2. Expect: USB: DFU
+9. `target_f2/deploy-dfu.sh` # load FW
+10.  # reboot device
+    1. Press right
+    2. Press left
+    3. Wait 0.1 s
+    4. Release left
+    5. Release right
+11. Wait 0.5 s
+12. # Expect FW
+    1. Expect: uart welcome message
+    2. Expect: USB Flipper CDC