Add refresh for views translations

To explain a bit more:

i18nstrings module introduces a 'refresh' op to hook_locale, through which existing strings in a given group can be read in en masse. This is useful if e.g. a user enables an i18nstrings-based module when there are existing data. The refresh functionality will process these data.

For views, we'd need to iterate through all existing views and process them.

Looking at ways to add localization directly to Views, which could make this issue unneeded.