Add new plotting functionality to 'sifting.py'.
Add an attempt at making a fancy, split-scale plot.

The better approach for doing this is by creating a custom scale.
Modify harmonic scrubbing to be more exacting.

The tolerance for two frequencies to be considered the same changes with harmonic number.

Also, added information about which harmonic a candidate is to the candidate's note. This information appears in the *.accelcands.report file.
Bugfix: was returning None instead of empty Candlist
Add split log-linear scale for when periods are used on the x-axis.
Fix typo in note for short-period bad cands.
Try to fix coordinates shown in interactive display.
Major changes to filterbank and routines using it for internal float usage
Added mjd_to_datestr() and beam_halfwidth() functions
Massive changes and simplifications for move to common backend format
Start changing the old PSRFITS struct to the new common spectra_info struct
Added new common backend files
Many more changes for unified backends...  broken, though.
Removed structure printing function.  Moved to common backend file.
Began changed for common backend format.  Lots still to do...
Merge branch 'master' into float_internals
Added printing functions for spectra_info structs
Updated all backend_common functions
More changes for common backend format...  ready to test
Initial changes for common backend format