#17 UserMaintenance component should clear the menu cache

[Gautam Jolly]

The menu options available to a user are dependent on
the roles. Hence when the roles are changed for a user,
then menu-cache should be cleared, so that they can be
re-evaluated. Make the appropriate change to
UserMaintenanceComponent, so that the menu-cache is
cleared only if changes are made to the logged-in user.

Additionally, the cached value of the
LabelEditHyperlink (see
TagHelper.ATTRIBUTE_LABEL_EDITOR_LINK_PREFIX) in the
HttpSession should also be cleared, since change of
roles may affect the access to the LabelEditor component.