views/timerange_select: escape keys and values

Escape keys and values of GET parameters before adding them
as hidden inputs in the time range form.

Without escaping, an XSS attack can be performed:
http://example.com/pnp/graph?host=a&srv=b&view=0"><script>alert("busted")</script>
(the host a with service b must exist)

Signed-off-by: Mikael Falkvidd <mfalkvidd@op5.com>