Added multi-data SPI Master supporting multiple sets of MOSI/MISO datalines.

app_spi_multi_data_loopback_demo implements a loopback test against several SPI Slaves (see app_spi_multi_data_loopback_demo README.txt)
Number of sets of MOSI/MISO data lines is configurable. Loopback test uses 2 sets but QSPI (4 sets) could be realised.
removed bin directory