Output excludes boundary fields from writing to the stream.
- boundary fields cannot be written because they are not defined in the bulk regions
- removed unnecessary method FieldSet::make_output_field_keys()
Sorption classes implement own EqData and input_type records allowing to give different names of output fields.
- removed rank test when equations set their output streams
New names of output fields.
- general scheme "subfield_multifield" applied, exception is when subfield has name ''
- current state:

  Flow: pressure_p0, pressure_p1, piezo_head_p0, velocity_p0
  Transport: A_conc
  DualPorosity: A_conc_immobile
  AdsorptionSimple/Mobile: A_conc_solid
  AdsorptionImmobile: A_conc_immobile_solid
  Heat: temperature

- tests are broken, new reference files will be in a separate commit
Fix CMake script generating rev_num.h: escaping double quotes in commit message.
Input key "data" changed to "input_fields" for all equations.
- con files updated
Add list of main changes in version 1.8.0

- may need update just before release
Reference manual - Reaction Term improved.
Cleanup of standard output.
Fixed makefile command for generation of flow_version.tex.
Sorption classes simplified. No ancestor of SorptionBase::EqData.
- the instance of EqData is allocated in constructor of derived class, where the name of output field is set
Applied comments of JB to pull request.
- methods returning const string changed to string
- SorptionBase::input_data removed
Updated reference tests.
- changes should be only in names of output fields + added section "Tensors" + values below tolerance
- timestep in test 03 changed from 0.01 to 0.1, so number of vtu files is reduced
- found bug in parallel run of Pade approximant (fails on Petsc error)
Fix GMSH output node and element indexing.
- labels of nodes and elements are now consistent with the input mesh so that results can be used as input data in further simulations
- test results will be updated in a separate commit
Updated GMSH reference results (numbering of nodes/elements may have changed).
Further simplifications in Sorption classes.
- init_from_input() made protected and called only from constructors of derived classes
- porosities are sent from DualPorosity to Sorptions within DualPorosity::set_porosity()
- SorptionBase::input_data_set_ moved to SorptionBase::EqData
- adsorption -> sorption on several places, this required changes in con files