Bug 1458

I've reworked the ns3 doxygen config, and some of the manual/tutorial/modules docs, to give a common look more in line with the ns3 homepage.  One thing I can't figure out is how to get waf to update a project version string in the various config files for the documentation.

Ideally I'd have waf use one of these rules:

- If it's an unmodified release (3.14), use that string

- Otherwise, use the parent directory name and changeset id.  For example, my last commit to my doxygen repo would be rendered as "doxygen @ 7905:3119c0c76657"

- If there are uncommitted mods, append a "+", or "+ 5 modified"

There are two files that need to have the resulting string updated.  It'd be nice to do the update in place, rather than have a template file with place holder that gets replaced to create the real file.  That is, 

In doc/doxygen.conf, update the line:
PROJECT_NUMBER         = "ns-3-dev"

In doc/ns3_html_theme/theme.conf (not part of ns3 yet), update the line:
projectnumber = ns-3-dev

Any ideas on how to accomplish this in wscript?

(See https://www.nsnam.org/bugzilla/﷒0﷓ for patch to build Sphinx docs, which would be a suitable place to edit theme.conf.)