Bug 21454: Do not require html filter on Price

Bug 21454: Do not require html filter on Price

Test plan:
- Apply first patch
- Confirm that tests is failing (t/template_filters.t)
- Apply second patch
- Confirm that tests return green
- Apply last patch
- Confirm that prices are displayed correctly

QA step:
Edit a template and add the following 2 lines:
[% SET p = '<script>alert("foo");</script>' %]
[% x | $Price %]
=> Display '0.00'

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>