Merge branch 'maint'
CBX support
OctoClock support
cbx: added entries into the manual
Merge branch 'mergeme/cbx'

Conflicts:
	host/docs/calibration.rst
	host/lib/usrp/dboard/db_sbx_common.cpp
Merge branch 'mergeme/octoclock'
Merge branch 'maint'
Merge branch 'maint'
Merge branch 'maint'
uhd: added virtual destructors for several interface classes
b100: switch to new packet demuxer
cbx: added support for cal utils
uhd: added new calls to streamer object + support work

* The transmit streamer gives access to the async msg queue.
* The receive streamer gives access to the issue stream cmd.
* Supporting usrp implementation files updated.
* Example applications updated to use this API.
uhd: conditionalize the eeprom check
usrp: automatic subdev spec for multi-usrp + helpful errors

The out of bounds checks will now have more helpful error messages thrown.
usb: added timeout param and additional queries
uhd: bump abi string for previous changes
uhd: packet demuxer, reset queue front b4 pop
usb: useful error messages on failed submit
usb: squashed thread related changes