Merged r10383:10390 from jcorgan/u2-wip into trunk.

Merged r10383:10390 from jcorgan/u2-wip into trunk.

* Implements daughterboard independent LO offset tuning

* Removes RFX specific LO offset code

* Adds 'set_lo_offset' to libusrp2 and Python API

* Adds --lo-offset to usrp2_fft.py and usrp2_rx_cfile.py

* Ensures daughterboards are reset to default values at
  startup.

Trunk passes distcheck.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@10392 221aa14e-8319-0410-a670-987f0aec2ac5