First commit (with some pseudo-code)

Started implementing server code for suggestion request, made mapper between user location and cluster coordinates, started creating new objects AutoGroup, Cluster and ClusterUserPair.
Changed DB schema and updated models accordingly

We no longer use AutoGroups and ClusterUserPair, but we updated the group and user tables instead.
start implementing groupSuggestion on server side
Fixed some stupid syntax errors and wrong use of request object
duplicated mapping function in group_views.py
This is an ugly hack and this function should be accessed from geometry library.
fixing the import of math functions...
fixing the missing constants
Merge branch 'groupSuggestion' of https://github.com/lca4/unison-recsys into groupSuggestion
Single-user mode
 - solo_views: changed generate_playlist method from GET to POST
Single-user mode

 - solo_views.generate_playlist: removes unnecessary with_user constraint in authentication
Single-user mode
 - adds prints to debug
Single-user mode

 - solo_views: removes with_user=True constraint in authentication
Single-user mode

 - solo_views: adds import plgenerator
Single-user mode

 - moves plgenerator to solo_views (for the tests)
Single-user mode

 - FIX 'é'
Single-user mode

 - removes unused import
Single user

  Fix typo
almost finished server implementation for suggestions.

Added an error constant, added referenceset on users on a cluster.

Warning, code not debugged
Fix some bugs in suggestion implementation and models.py
Single-user mode

 - solo_views.plgenerator: now handles options
 - schema.sql: added seeds specific fields in playlist table; removes local field from pllib_entry;
   changed ratings default value to -1