TPac: locale handling improvements

TPac: locale handling improvements

Allow Locale::Maketext to fall through to parent locales
(superordinate) when the a translation for a string in the given locale
is not present.  Locale::Maketext suppports arbitrary-length locale
tags, so it's possible to create locale hierarchies.

For example, you could create branch-specific translations that fall
through to system, then full locale, then base locale, then the default
template strings.

en_us_systemA_branchX => en_us_systemA => en_us => en => <template strings>

Each template string that needs translating will be tried against each
locale in order until it finds a translation.

Signed-off-by: Bill Erickson <berick@esilibrary.com>