activate storage also for sub models
activate storage also for sub models


Former-commit-id: 5d1c915d8551512268e6e2245f7fd6278b1c5c5a
danielhers/dynet,clab/cnn,shuheik/dynet,shuheik/dynet,clab/dynet,clab/dynet,clab/dynet,xunzhang/dynet,shuheik/dynet,xunzhang/dynet,shuheik/dynet,chunyang-wen/dynet,clab/dynet,danielhers/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,clab/cnn,shuheik/dynet,clab/dynet,danielhers/dynet,xunzhang/dynet,clab/cnn,danielhers/dynet,danielhers/dynet,chunyang-wen/dynet,chunyang-wen/dynet,chunyang-wen/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet