FPGA: The second receive channel has been made fully independent.

Some registries require changes in HOST code.

Conflicts:
	fpga/usrp2/top/N2x0/u2plus_core.v
FPGA: The second transmit channel was added.

Some registries require changes in HOST code.
FPGA: Multiplexer for the RX and TX frontends was added.

This was done due to the fact that the host can be able to work in dual channel mode.
FPGA: Work of each DSP channel's is indicated by separate LED's

LED A - Indicates the transmit status of the first transmit channel (LMS1)
LED C - Indicates the receive status of the first receive channel (LMS1)
LED E - Indicates the transmit status of the second transmit channel (LMS2)
LED B - Indicates the receive status of the second receive channel (LMS2)
FPGA: Fix control logic for the Spartan 6 ICAP
FPGA: AUX connector. I2C bus was added.
FPGA: AUX connector. SPI bus to ADF4350 was added.
FPGA: AUX connector. Pins to AUX connector were uncommented.
FPGA: AUX connector. Control logic for Lock Detect was added.