reduced verbosity for missing atoms
update script, more cross platform

* Update OpenStructure compounds.chemlib if OpenStructure is found.

* Replacing the code to update OpenStructure compounds.chemlib with a call to its internal script.

* Implementing more flexible approach allowing notifying all dependent software.

const versions of find

update unit-test for create_nonpoly

extended nonpoly unit-test

added compare functions for Datablock and Category

do not throw from Category::isValid()

install update script (optionally, unix only)