Examples are installed by default to "docdir", which refers to
PACKAGE_TARNAME variable which was empty for the python plugin Makefile.in
So the examples were installed to '.../share/doc/examples' instead
of '.../share/doc/sudo/examples'. This also made them be skipped from the
package.
Also the install target now depends on install-doc so the examples
gets installed also (similarly as other examples).
If non root can alter any imported python modules, he is able to run
anything he would like to as root user.
This class is a helper to avoid such situation.
This feature can be disabled with 'DeveloperMode=1' plugin option.
