Add Catalan translation
Fixes to Catalan translation
Updated Hebrew translation
Prevent gnome-autogen.sh from overwriting custom INSTALL file
Update translation comments to assist translators

Quick Add words can be a little tricky for translators, so attempt
to help with a little clarification as well as use the same ALL CAPS
terms as in the wiki page on Quick Add translation.
Updated Brazilian Portuguese translation
Add link to TranslatingQuickAdd wiki page in PO file comments

Wiki page is to assist translators who have trouble with words used
by Quick Add parser.
Merge branch 'master' into wip/calendar-spans
Cleaned up Calendar class heirarchy

A cleaner inheritance tree: Span at the bottom for all date-
oriented classes, DiscreteUnit for well-recognized units,
UnitSpan for groupings of those units, both Spans.  Less reliance
on interfaces.
Further cleanup of UnitSpans, added YearSpan
Consolidate Iterable into UnitSpan
DiscreteUnit -> Unit
Emphasize Spans, not DateSpans, in Calendar interfaces