Firmware panic

**Feature description**

Add ability to freeze firmware execution

**Is your feature request related to a problem? Please describe.**
If critical crypto conditions detected then device should be locked to prevent access to coins and preserve funds in wallet.

**Describe the solution you'd like**
Implement a function that relies on built-in device traps to halt device execution .

**Describe alternatives you've considered**
Setting a flag in order to exit main loop gracefully , might be hijacked (i.e. flag value reverted after failure detected but prior to loop conditional).

**Additional context**
Skycoin core panics if some (serious) crypto errors are detected at run time . This is to protect coins . Firmware does not support doing so .

**Possible implementation**

- [x] Add `void panic(char *)` in `error.h`
- [x] Trigger `EXTI0` ISR from software so as to abandon stack execution context right away and enter an infinite loop in the end
- [x] Send `Failure` message with `Failure_FirmwarePanic` reason
- [ ] Replace inline `TODO` comments related to `abort()` in `skycoin-api` with a call to `panic()`
- [x] Implement firmware panic for emulator by displaying error message and disabling all interaction