Release 2.0.0 (intrig#6)

Merging v2.0.0. from dev.

* ready to make xenon namespace

* broken

* prog with new ns

* xenon converted to xenon namespace complete

* oops, not quite

* Continue port to xenon namespace

Renamed include/ict to include/xenon.
Copied a couple ict files over to ict repo.
Still have to purge ict files from xenon and their unit tests.

* prog

* prog with exceptions

* prog

* ict::exception removed

* prog with xml_error

* ready to add ict submodule

* added ict submodule

* prog

* minor

* updated copy

broke out find_functions.h