luci-base: dispatcher: support raw values in attr() and ifattr()

luci-base: dispatcher: support raw values in attr() and ifattr()

Extend the attr() and ifattr() template functions to take an optional
further parameter indicating that the passed value should not be escaped.

This is needed for cases where the input already is escaped through
other means, e.g. when the value was previously filtered through the
striptags() template helper.

Signed-off-by: Jo-Philipp Wich <[email protected]>
(cherry picked from commit 4141243762aafb7960d67f871c97907307005f87)