adding C++11-threads-based concurrency
fixing std::ref issue in cxx11_thread
adding missing member functions to shared boundary condition
Merge pull request #159 from mwarusz/master

new subgrid solver and some fixes
fixing unitialised value bug in concurr::sumtmp
Merge pull request #158 from slayoo/concurr_cxx11

adding C++11-threads-based concurrency
Merge pull request #161 from slayoo/concurr_sum_uninit_fix

fixing unitialised value bug in concurr::sumtmp
resolving conflict; updating to be mergable with master