* Add bootstrap-autogen depdenency to lint target to force
generated files to be created.
* Add validate-src-strings to lint rules
* Add validate-src-strings as dependency to lint targett
* Remove obsolete test_lang frm test target
* Add diagnostic message to validation command in i18n.py
that outputs how many objects were scanned. Formerly it only
output a message if there were errors. This made it impossible to
distinguish an empty file from one with no errors.
* While adding the validation counts it was discovered plurals had
been omitted for some of the validation checks. Added the missing
checks for plural forms.
* Also distinguished between errors and warnings. Permit warnings to
be emitted but do not fail the validatition unless actual errors
were also detected.