update NEWS and other docs in preparation for 1.8.0rc1

update NEWS and other docs in preparation for 1.8.0rc1

in particular, merge the various 1.8.0b1/b2 sections, and remove the
datestamp. NEWS gets updated just before a release, doesn't need to precisely
describe pre-release candidates, and the datestamp gets updated just before
the final release is tagged

Also, I removed the BOM from some files. My toolchain made it hard to retain,
and BOMs in UTF-8 don't make a whole lot of sense anyway. Sorry if that
messes anything up.