A lot of changes.

Created an external serial class with custom events, a communication
stack class for parsing input frames/generating output frames, and
dicked around with RSA implementation with a variable key size (>128 bit
due to padding).  RSA implemented with provided libraries/services.
Encryption is done 1 block at a time, rather than a single character at
a time, hopefully improving efficiency.   Block size recalculated
depending upon key width.