s/NeubotFoo/IghtFoo/g

Pass one of the renaming effort: deal with all the symbol
names starting with Neubot.
s/NEUBOT/IGHT/g

Pass two of the renaming effort: deal with the names that
include the NEUBOT string.
s/neubot_/ight_/g

Pass three of the renaming effort: replace all the occurrences
of `neubot_`.

Leave for later other strings containing `neubot`.
Do a couple of s/neubot/ight/gi

The places where to replace were selected by looking at
the output produced by grep.
mv libneubot.json libight.json

And propagate changes (in particular, make sure that config.local
picks up the new name rather than the old one).
mv libneubot.py _libight.py

Also, propagate changes in config.local and in test/*.py.

The new name starts with underscore because the autogenerated
file is not so easy to use.
README.md: s/libneubot/libight/ and update description
More consistent ight_wrappers.h ifndef-guard name
Fix a couple of wrong s/neubot/ight/ in comments

I did the big rename, then checked the aftermath, to fix cases
in which the s/neubot/ight/ was wrong.

I missed a couple of cases, which I fix with this patch.

While there, also fix small errors in other comments.
Libight is more readable than LibIght

Especially for fonts in which the uppercase i letter looks
like the lowercase l letter.
Merge pull request #5 from bassosimone/rename-all

Rename all (the "neubot" prefix becomes "ight")