Replace 'Av.' with 'Avg'.

The latter is more widely known than the former.
Fix copy'n'pasto.
Unbreak id attribute.

Id attribute is unique. Each time an id is used in an element it must
have a different value.
Name is pgBadger.

The software is named pgBadger. Fix some places that call it PgBadger (p
is lowercase).
Forgot to replace PgBadger in a few places.
Merge pull request #80 from eulerto/master

Trivial fixes