FieldSet setters affect fields added after.

- FieldSet methods: set_mesh, set_intput_list, set_limit_side
  store values and set them to the fields added after call of the setter

- input/accessors.hh, need is_empty() method for Array; should be in
  common parent class

- fix possible double delete of data in FieldElementwise
Fix test 22
- add fields for new output
- fix ref_output, previous version
  did wrong output of velocity and divergence error
  (computation of divergence error is still wrong,
   however we output right array)
Merge branch 'output_master' of github.com:flow123d/flow123d into output_master
Add MPI rank EI to exceptions generated by ASSERTs.

- add mpi rank inforamation to internall error messages, should be done
   also for xprintf, useful for parallel debugging,
TimeGovernor::view() use just Msg message type

- in fact it is not debugging mesage, MsgDbg should be used just
   through DBGMSG maccro, otherwise it could be interchanged with
   debugging output
- add conditional call of the view function where it is used
FieldElementwise - add constructor from std::vector
FieldSet - check for duplicit addition

- operator += check if the field is already present in the field set
- internal method field_by_name
- add safety assert in field_impl
OutputTime can be constructed an all processors

- remove some rank tests so that we allow construction of OutputTime
  classes, but open the file and perform output only on master process
Fix output for DarcyFlow

- support standard output fields and error fields
- support output of subdomain indices
- some simplifications
- fix destructor
Input field set added in DualPorosity and SorptionBase to distinguish fields that are read and set.
Merge branch 'output_master_new' into output_master

Conflicts:
	src/flow/darcy_flow_mh_output.cc
	src/reaction/sorption_base.cc
	src/reaction/sorption_base.hh
Fix infinite loop in TimeMarks::add_time_marks() caused by zero dt.
- In that case only the initial time mark is added.
Implemented methods in Input::Type::Selection.
- copy_values() to add values from another selection
- int_to_name() to access value names by id
Changed input format for equation output.
- primary and secondary equation specify their output stream and an array output_fields indicating which fields will be saved
- equation informs the output stream about fields that are to be saved
- key save_step renamed to time_step and moved to output_stream record
Fix is_constant in FieldSet - all fields must be constant to return true.
Add initial condition in sorption and fix substance indexing.

- initial condition added in sorption for sorbed concentration
- bug in local substance indexing revealed and solved
Fix - method 'emplace' not in gcc4.7 (C++11).
Merge branch 'PE-reactions-output' into output_master