[exercises-fractures-properties-mainfile] naming conventions

exercises/exercise-fractures/CMakeLists.txt

exercises/exercise-fractures/README.md

exercises/exercise-fractures/main.cc

exercises/exercise-fractures/params.input

exercises/exercise-mainfile/CMakeLists.txt

exercises/exercise-mainfile/README.md

exercises/exercise-mainfile/exercise1pamain.cc

exercises/exercise-mainfile/exercise1pbmain.cc

exercises/exercise-mainfile/exercise1pcmain.cc

exercises/exercise-properties/CMakeLists.txt

exercises/exercise-properties/README.md

exercises/exercise-properties/main.cc

exercises/exercise-properties/params.input

exercises/solution/exercise-fractures/CMakeLists.txt

exercises/solution/exercise-fractures/main.cc

exercises/solution/exercise-fractures/params.input

exercises/solution/exercise-mainfile/CMakeLists.txt

...s/solution/exercise-mainfile/exercise1pa_solution_main.cc

exercises/solution/exercise-properties/CMakeLists.txt

exercises/solution/exercise-properties/main.cc