tpac translations broken in 2.9

Evergreen 2.9 / master

When we merged bug 1484650 for webstaff translations, it looks like I made an error with the Makefile process. In the build/i18n/Makefile, around lines 366, we see:

        mkdir -p $(TT2_DATA_DIR)
        cp $(PO)/tpac/$(LOCALE).po $(TT2_DATA_DIR)/.
        cp $(PO)/webstaff/$(LOCALE).po $(TT2_DATA_DIR)/.

Which because the files are named the same for a given locale (like cs-CZ.po), this means we are overwriting the tpac po file with the webstaff po file during the translation process.

This leads to a situation like described on the mailing list by the Czech users (see: http://markmail.org/message/vvr33px2rza4un46 ) where their TPAC doesn't show any translations, because there aren't the right string matches.

The solution I think is to break up the TT2_DATA_DIR into separate entries, one for TPAC proper, and one for webstaff. Right now, it's only TT2_DATA_DIR=../../Open-ILS/src/data/locale. Perhaps those should be further subdivided to locale/tpac/* and locale/webstaff/*, or make them entirely separate defined variables. Or leave the TPAC one alone, but define the Webstaff data dir somewhere else.

Either way, we should update the included apache config examples in eg_vhost.conf. And possibly update the translations setup in documentation too, like in http://docs.evergreen-ils.org/2.9/_setting_a_default_language_and_adding_optional_languages.html

Working branch to follow. Thoughts or opinions on approach?