Support for HID-based partial super-fast flashing (#523)

* fix bug

* Fixed an issue where the Game of Life menu item was not appearing (#497)

* Starting on dapjs flashing

* Adding dapjs

* Connected

* Flashing works

* Double buffer flashing

* Add SHA computation function

* Run SHA code

* Swap SHA for murmur+crc

* Switch to dual murmur3

* Partial flashing works

* Remove unused code

* Move flashing code to external/sha

* Fix whitespace

* Cleanup binary genration scripts

* Add docs for hid flashing

* bump pxt-core to 0.12.132,

external/sha/.yotta.json

@@ -0,0 +1,6 @@
+{
+  "build": {
+    "target": "bbc-microbit-classic-gcc,*",
+    "targetSetExplicitly": true
+  }
+}