Starting sensor support

TODO.md

@@ -1,6 +1,11 @@
 * [x] try unlink ELF file before uploading - didn't work
 * [x] implement serialPoll
 * [x] try some motors
+* [ ] add `control.interrupt(ms, () => { ... sync function ... })` - running outside regular JS thread
+* [ ] add `//% onlyWhenUsed` on global variable initializers
+* [ ] parse Python field lists into offsets
 
 ## Further down
 * [ ] have some protocol for restarting user app if it's running (flag file somewhere?)
+* [ ] display panic code on the screen
+* [ ] catch SIGSEGV and panic