- add Changelog for 2.0 release
- Make dtplite configurable in Makefile, e.g.
     make "DTPLITE=/usr/local/ns/bin/tclsh8.5 /usr/local/ns/bin/dtplite" man

- regenerate documentation
- bump verison number to 2.0 (also in .man files)
- set the right version number to 2.0.0