Add clang-format file

Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.

LibCore/CProcessStatisticsReader.h

@@ -24,6 +24,6 @@ public:
 private:
     void update_map(HashMap<pid_t, CProcessStatistics>& map);
     String get_username_from_uid(const uid_t uid);
-  
+
     HashMap<uid_t, String> m_usernames;
 };