Global code search support (#3664)

* add global code search on explore

* fix bug when no anyone public repos

* change the icon

* fix typo and add UnitTypeCode check for login non-admin user

* fix ui description when no match

options/locale/locale_en-US.ini

@@ -169,9 +169,12 @@ repos = Repositories
 users = Users
 organizations = Organizations
 search = Search
+code = Code
 repo_no_results = No matching repositories have been found.
 user_no_results = No matching users have been found.
 org_no_results = No matching organizations have been found.
+code_no_results = No matching codes have been found.
+code_search_results = Search results for "%s"
 
 [auth]
 create_new_account = Create Account