fix 'hf iclass reader'

* code deduplication. Use functions from iso15693.c
* speedup CodeIso15693AsReader()
* invert reader command coding. 0 now means 'unmodulated' ( = field on)
* decode SOF only as a valid tag response in Handle15693SamplesFromTag()
* complete decoding of EOF in Handle15693SamplesFromTag()
* determine and write correct times to trace
* FPGA-change: generate shorter frame signal to allow proper sync in StartCountSspClk()
* modify StartCountSspClk() for 16bit SSC transfers
* whitespace in util.c
* add specific LogTrace_ISO15693() with scaled down duration. Modify cmdhflist.c accordingly.
* allow 'hf 15 raw' with single byte commands
* check for buffer overflow, card timeout and single SOF in 'hf 15 raw'