Initial library

Initial release of kpn532 as a lib, with examples:

• library must be downloaded from the git or tag, then decompressed to Arduino/libraries (you must have a directory named kpn532) ;
• kpn532_relay can be built from examples, binaries are below
  • v0, verbose = 0 (minimal output)
  • v1, verbose = 1 (exchange traces)
  • r0, raw = 0 (ISO / DEP, with WTX)
  • r1, raw = 1 (raw exchange)
• kpn532_st25tb can be built from examples, binaries are below