Use help2man to generate man pages (fixes #165)

A little more lightweight than the doxygen approach,
and keeps the documentation harmonized with --help.

h/t to A. Maitland Bottoms for pointing me to this.
libbladeRF: Corrected documentation commands in README.md
bladeRF-cli: Added a clock_gettime() implementation for OSX
Merge branch 'dev-issue165-use-help2man-rev3' from https://github.com/rtucker/bladeRF
host: Added option to disable "warnings as errors" in builds

Developers should always build with -Werror or /WX. However, we've had a
few cases with different compiler versions throwing errors that devs
didn't see, breaking master for users. The intention of this change is
to give those users a quick workaround, rather than requiring them to
hack around the warning in the source.
host: Updated README.md to include CMake TREAT_WARNINGS_AS_ERRORS option
Adding time.h for timespec.
Fixing time getting for OSX.
common: add BE32 <-> HOST endian conversion
common: Add sha256 code from FreeBSD
libbladeRF: Supporting changes for backup/restore of flash

- Verify flash pages as they are written
- Add function for initializing the calibration region in flash
- Add functions to read/write flash images with sha256 and metadata
- Add support for unaligned read/program
bladeRF-cli: Add backup and restore commands

Usage:

```
bladeRF> help backup

backup <file> [address,len]

Backup a flash data to a file.
   `address'     defaults to the address of the calibration data.
   `len'         defaults the size of the calibration data  (256 bytes).

bladeRF> help restore

restore file [address,len]

Restore flash data from a file.

   <address>   defaults to the address of the factory calibration data or the
               address stored in the metadata section of the image if it exists

   <len>       defaults the size of the factory calibration data (256 bytes) or
               the length of the image given
```
bladeRF-cli: Add init_cal command

Initializes the calibration region in the flash

Usage:
```
bladeRF> help init_cal

Initializes the calibration region in the flash with new values
init_cal fpga_size vctcxo_trim

   <fpga_size>       Either 40 or 115 depending on the device model.
   <vctcxo_trim>     VCTCXO/DAC trim value (0x0-0xffff)
```

Conflicts:
	host/utilities/bladeRF-cli/src/cmd/cmd.c
Add debian/copyright entries for new code
bladeRF-cli: Help text and error message touch-ups
libbladeRF, bladeRF-cli: Simplified flash image format and handling

These changes simplify the image format a bit; the metadata fields are
flattened into the image to simplify both image creation and manually
viewing/extracting contents from images.

The checksum has been moved to directly after the file format's magic
value (i.e., signature), to make it a bit easier to just extract data
via dd. Similar to the approach used by mkimage for U-Boot headers,
the checksum calculation is performed over the entire image, with the
checksum field zeroed out.

Touched up CLI backup/restore commands and separated <address>
and <length> to separate args.
bladeRF-cli: Added flash_image command and alphabetized commands
bladeRF-cli: flash_image timestamp shown in human-readable format
bladeRF-cli: Split backup and restore commands, misc cleanup
libbladeRF: Fixed length of FPGA region of flash in API header