Remove type prefix and single quotes for URL literals of types Date, DateTimeOffset, Guid, and TimeOfDay

Currently we require literals for e.g. Date and DateTimeOffset to be prefixed with a type identifier, e.g.

$filter=StartDate ge date'2013-09-02'
$filter=ChangedAt lt datetimeoffset'2013-09-02T00:00Z'
$filter=EndTime lt time'23:59'
$filter=ID eq guid'01234567-89ab-cdef-0123-456789abcdef'

~/Tasks(guid'01234567-89ab-cdef-0123-456789abcdef')

In most cases the type of the literal can be deduced from the context, e.g. type of other comparison operand.

The only case in which this cannot be done is when comparing two literals, which is rare.

So we can make the prefixes at least optional, or even completely get rid of them