fix dependency issue and add Chinese Language Support

[iWangJiaxiang]

Hi, there are following changes:

1. Fix dependency conflict that may be annoying in container situation.
2. Add Chinese Language Support.
3. Fix null method error when no role mappings set on the SSO provider side.

When no role mapping assigned to the user, it would cause 500 error when logged in. The log shown help me to find the reason but still cost much time. I just add a logic to solve the problem for other users.

App 14806 output: I, [2019-08-28T01:58:47.343736 #14806] INFO -- : Completed 500 Internal Server Error in 197ms (ActiveRecord: 121.6ms)  
App 14806 output: F, [2019-08-28T01:58:47.344390 #14806] FATAL -- :  
App 14806 output: F, [2019-08-28T01:58:47.344444 #14806] FATAL -- : NoMethodError (undefined method `include?' for nil:NilClass):  
App 14806 output: F, [2019-08-28T01:58:47.344470 #14806] FATAL -- :    
App 14806 output: F, [2019-08-28T01:58:47.344493 #14806] FATAL -- :  plugins/redmine_openid_connect/app/models/oic_session.rb:143:in `admin?'  
App 14806 output: plugins/redmine_openid_connect/lib/redmine_openid_connect/account_controller_patch.rb:140:in `oic_local_login'  
App 14806 output: lib/redmine/sudo_mode.rb:63:in `sudo_mode'