Flash programming partially works

- eb/etherbone.py: python API wapper using Etherbone libaray
- eb/eb.py: xil_multiboot device class with direct register access
- flash_m25p.py: M25P flash IO class
- xil_multiboot.py: top class that supports all ICAP/flash on target
- mbtest.py: __main__ test script that proofs a successful flash reading & erasing

Finished building chains to implement bit file generation using data2mem. Refer to http://www.ohwr.org/issues/1006

Added tools/eb-*.c for Etherbone support of wrc console, info & flash programming.

Added impact script for JTAG bit file programming.

Updated README.md