Fix jinja template error reporting
Fix jinja template error reporting

This fixes a problem where the wrong line number is reported when there
is an undefined jinja variable. It also provides context to pinpoint the
location of the bad line.

There is also additional cleanup here, the SaltTemplateRenderError class
is removed in favor of the new SaltRenderError, and
get_template_context() has been removed, since it has been moved to
salt.utils.get_context().

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt