BSP update

- Add basic LED BSP
- Moved generic examples to the HAL
- Updated rust edition to 2021
- Updated README to provide full instructions for flashing and building
- Added jlink.gdb file to command line flashing

examples/blinky-button-irq.rs

@@ -0,0 +1,18 @@
+//! Minimal blinky for the REB1 board using only PAC features
+#![no_main]
+#![no_std]
+
+use cortex_m_rt::entry;
+use panic_halt as _;
+use rtt_target::{rprintln, rtt_init_print};
+use va108xx_hal::pac::interrupt;
+
+#[entry]
+fn main() -> ! {
+    rtt_init_print!();
+    rprintln!("-- Vorago Button Blinky --");
+    loop {}
+}
+
+#[interrupt]
+fn OC15() {}