ConvectionTransport must match input times

- force ConvectionTransport to meet times in which any of its data change
- add test to test 14, with short concentration pulse
Fix unit_tests/system/exceptions

- make quick hack in system/global_defs.h
  to optionally turn off MPI support in ASSERT
- TODO: needs more robust implementation, see comment there
Merge branch 'output_master' of github.com:flow123d/flow123d into JB_time_dependent
Ref. doc. update - quick start, usage

- update section Quick Start
- update section How to run the simulation
- add default values to arguments -i and -o
Merge branch 'output_master' of github.com:flow123d/flow123d into output_master