Introduce server-side validation for HTML5 date and time formfields
A "formats" parameter can be specified on the formfields indicating one or more formats that we want to enforce. The syntax for any of such format is that of the Tcl clock command. Default values have been set according to the expected behavior of each form field type. Empty values are always considered valid. If a field is required, this will be enforced in its own validator.
Fixed unreviewed commit, which might lead to hard-to-spot errors
The last change assumed that "nls_language" can be hard-wired to contain most 5 characters. While this not backed by the OpenACS data model, the standard (RFC 5646) explicitly states that there is no upper limit on the size of language tags. The tree letter language codes have been standard since 2001 (RFC 4646).
The change accepts now all defined locales. When the specified locale is not enabled, it provides a log notice, when the locale is not defined at all, it provides a warning and falls back to "en_US".