classifier: add `set_label` and `get_labels` for fix #655
cpplint ok
local_storage_mixture::set/get_label(s) is tested by `storage_test.cpp`
add setter/getter of cluster name, fix #668
Merge pull request #707 from jubatus/feature/setter_getter_of_clustername

add setter/getter of cluster name, fix #668
set_label() should return boolean instead of integer
Merge pull request #706 from jubatus/feature/set_get_labels

setter/getter of labelset in classifier
jenerated by old generator
client was generated by old jenerator