MLRsearch: Support other than just two ratios

+ Change some method names and argument types:
 + Do not mention NDR and PDR, except as examples.
 + Return list of ReceiveRateInterval instead of NdrPdrResult.
 + The resulting intervals can be degenerate when hitting min/max rate.
+ Rename quantity name parts from "fraction" to "ratio".
+ Intervals are no longer tracked for each target ratio.
 + They are found dynamically from known results.
+ Add effective_loss_ratio field to avoid loss inversion effects.
+ Move some functions to separate files.
 + Bound search logic moved to MeasurementDatabase.py
 + ProgressState moved to its file.
 + WidthArithmetics.py holds small computation functions.
+ Use parameter expansion_coefficient instead of "doublings".
+ Do uneven bisect to save time when width is not power of two times goal.
+ Timeout now correctly tracked for the whole search,
  not just the current phase.
+ Make logging (debug) function pluggable.
 + Added debug log messages for initial phase.
+ Do not mark as subclass if contructor signature differs.
+ Avoid re-measure on scale-limited (ASTF) profiles.
+ Remove outdated comments.
+ Bump copyright years.

Change-Id: I93f693b4f186f59030ee5ac21b78acc890109813
Signed-off-by: Vratko Polak <vrpolak@cisco.com>