add validation db in developement config file to fix run time err
PDIO-188 #comment change user and item API to new format
PDIO-188 #comment add unified u2iActions API
PDIO-188 #comment take out attribute ct in get user and get item response
PDIO-189 #comment flatten items/users custom attributes and add prefix "ca_" when store into mongo
PDIO-189 #comment change u2iaction action field to string. remove evalid from u2iaction.
separate like and dislike action by name (instead of using v field).
PDIO-190 #comment change action field to string and separate like and dislike actions
PDIO-188 #comment add prefix pio_ for itemRecTopN API predefined attributes
PDIO-188 #comment rename pio_tiid to pio_iid
PDIO-188 #comment keep legacy API (no prefix pio_) for pixel tracking
PDIO-191 #comment migrate appdata to new format
(don't handle u2iaction evalid since it's never written)
Merge branch 'custom_action' into develop
Merge branch 'develop' of github.com:PredictionIO/PredictionIO into develop