Don't auto-tag partial matches.

Add `import: confirm_partial` setting, with a default of "no" (current
behaviour). If set to "yes", strong recommendations for partial matches will
be downgraded to medium recommendation, thus will require confirmation and
will not be auto-tagged.
Safer defaults on confirmation prompts.

Remove default option and require selection on confirmation prompts for:

- Partial matches, if `import: confirm_partial` setting is "yes".
- Matches that are below the medium recommendation threshold, but above the
  gap threshold.
- Matches that have no recommendation.
- Matches other than the best and auto-suggested match.
For matches with no recommendation, import as-is or skip automatically.

Add `import: none_rec_action` setting with a default of "ask" (current
behaviour). If set to "asis" or "skip", matches with no recommendation will be
imported as-is or skipped automatically.
Align LHS and RHS changes. Put track/duration differences on RHS.
Add docs for `none_rec_action` setting.
Add docs for `confirm_partial` setting.
Working smart playlist plugin
Fix optional relative_to
Add print statements
Add comments
Change command to splupdate
Add documentation for plugin
Fix playlist_dir not resolving relative path
show media in candidates disambiguation
Add ability to use tag in m3u names
Documentation about template in m3u names
Fix tests.
Add default for playlist_dir
Remove debugging statement

Silly me for forgetting to check the pdb statement I just put in ...
Merge pull request #78 from mrmachine/align-changes

Align LHS and RHS changes. Put track/duration differences on RHS.