Modifications of output writers for compatibility of reference results
- fields ending "_p0" or "_p1" renamed to "_elements", resp. "_nodes"
- NumberOfComponents dropped for scalar fields
- tensor fields omitted
Fix of output time for steady flow.
- time inf changed to 0 in output writers
New output for Darcy flow.
Fixed output in transport classes.
- ConvectionTransport: output field names appended with "_mobile" for compatibility of reference results
- fixed parallel code
Fix reading tensor values from input.

- fix in fields/field_values.hh
- better coverage in field_const_test
Use std::string to pass EI_Address info.

... until we have Address class that persist after destruction of
the root input accessor.
Test output of all fields in 3D.

- minor simplifications in output*
- OutputTime::clear_data() is proper member and clear only
  data of particular object;
- move OutputDataBase declaration to separate file, necessary for tests
- implement correctly output of fields returning Fixed vectors
  and tensors of 2D space

- exception for variable size vectors
Merge branch 'JB_output_fields' into output_master
Fix callto uninitialized mass balance object in ConvectionTransport.
Fixed con files in test 20 - output key "conc_mobile_p0" changed to "mobile_p0".
Rename immobile concentration matrix in dual porosity.
Rename DualPorosity class.
Fixed reference test 21.
- units for temperature temporarily changed to M/L^3
- name of output field in con file updated
Updated con filed for test 23 (output field conc_mobile_p0 changed to mobile_p0).
Sorption output - sovled by renaming substances.
Merge branch 'output_master' into PE-reactions-output.

- outputs in dual porosity a sorption is ready
- output in linear reaction is not available
- all outputs in reactions are 'optional'
- output names are ready to name convention
- new outputs in con files - test20, 23 are commented, can be enabled easily

Conflicts:
	src/io/output.h
	src/transport/transport.cc
	tests/23_dual_porosity/dual_por.con