cleaned and re-organized Priority_Context
cleaned and re-organized Priority_Context

worker and queue are in separate objects, fixed memory management.

nbruns1/metaSMT,hoangmle/metaSMT,agra-uni-bremen/metaSMT,finnhaedicke/metaSMT,agra-uni-bremen/metaSMT,agra-uni-bremen/metaSMT,nbruns1/metaSMT,nbruns1/metaSMT,hoangmle/metaSMT,finnhaedicke/metaSMT,finnhaedicke/metaSMT,hoangmle/metaSMT