Minor improvements in build and test system.

- ignore *.orig
- *.tst rules in tests directories; to run only one con file
- commented recepie to coberture usage (cover testst)

Conflicts:
	unit_tests/system/tokenizer_test.cpp
More specific subtests of test 20.

covered:
- old adsorption code
- new code using tables
- new code with spatialy variable param, use non-lin solver
  directly
- all three isotherms

missing: limited solubility, concentration out of table
Optimization and polishing of isotherm.*

- remove unnecessary stuff
- some inlining to narrow critical code points
- improved class documentation
- necessary changes in sorption.cc and transport.cc