Introduce new dynamic library loader: dl_loader
dl_loader: add load_func_ptr template function
Use std::system_error for handling system errors

 Now planet::exception_errno dropped
Reasons:
std::system_error is highly customable and functional
Preventing reinventing the wheel
Merge branch 'ltdl_to_load' into develop

* Use libltdl for loading external module
* Use std::system_error for error handling
Add some uncommited files