Convert CLI to cmdliner, begin CHANGES

A number of command-line processing changes including switching -l/--local to --remote, -p/--prefix to --prefix, changing the default prefix to / rather than the output directory, and making access log parsing optional
Don't include the built Version module
Fix version interface bug
Update README with new cmdliner dep, changed CLI options, fixes OCamlPro/opam2web#46
Ignore autogenerated version.ml
Move packages and their versions into a path hierarchy; drop 'index.html' where it would be inferred
Make Home page absolute '/' and fix O2wTemplate.prepend_root to respect absolute paths
opam2web version/revision and dirty flag are now exposed in meta generator
Merge cmdliner for meta generator feature
Merge pull request #47 from dsheets/cmdliner

Convert CLI to cmdliner, begin CHANGES
Basic tag predicate support
Extract page template and repo index into templates; implement simple XML template system
Merge branch 'preds' into template

Conflicts:
	CHANGES
	src/o2wRepository.ml
	src/opam2web.ml
--pred is now --where
CHANGES
If no files to generate stats are provided, don't generate stats
Merge pull request #50 from dsheets/template

Indexes, Predicates, Templates
Fix API changes
A quick & dirty hack to generate only the HTML pages of packages satisfying --where
Merge pull request #51 from samoht/less-HTML-pages

Generate less HTML pages