added initialization support of rnnlm from list of expression
added initialization support of rnnlm from list of expression

Peilun-Li/dynet,Abasyoni/dynet,Abasyoni/dynet,Abasyoni/dynet,dhgarrette/cnn,cherryc/dynet,Peilun-Li/dynet,dhgarrette/cnn,dhgarrette/cnn,kamigaito/cnn,mitchellstern/dynet,Peilun-Li/dynet,cherryc/dynet,cherryc/dynet,kamigaito/cnn,mitchellstern/dynet