general-cores: updating gencores to use wb_streamer
etherbone-core: added as submodule
top: Added Etherbone support.

- Added Etherbone core as wishbone master in top crossbar.
- Added a multiplexer to connect Etherbone and Nic core to wr-core.
- Connected wr-core to Etherbone configuration space to access Etherbone registers.
- wrc.ram: Updated with Etherbone support. (Old: wrc_without_etherbone.ram)
- wrc.ram: Updated ep_pfilter for Etherbone packets. You can see this configuration in extra folder.
dio: Added DIO ch0 input support and hold DIO ch0 output as 1-PPS dedicated signal. Deleted PPS mode in DIO core
dio leds: Connected and working.

- OUT is enable when one pulse occurs or 1-PPS ch0 signal is enable.
- TERM enable when any resistor termination channel is enable
wrc.ram: Updated to last version with Etherbone support. Copy ep_pfilter with etherbone to extra folder.
doc: Updated project doc

	- Updated WR-NIC architecture diagram (dia file uploaded too)
	- Changes in doc/wr-nic.md to update information
		- Channel 0 output is dedicated for 1-PPS signal
		- P mode removed from DIO configuration registers
		- Added new section about remote configuration with Etherbone
		- Initial channel configuration is changed
		- Updated LM32 firmware generation
dio: correct doc and comments for first channel (ch0) mode

The first channel is set with 0 so that we force it to be output mode
p/P & i/I mode will be only available for ch0, and D,d,1,0 will not be
working (they will be seen as p/P).