[postgis-devel] Translation updates

[Sandro Santilli]

FYI: I've added the missing translation file for
reference_temporal.xml to transifex, updated al .pot files
and updated the transifex configuration to try at having it
automatically update .pot files from github.

It's still not fully clear to me what the procedure should be
but this is something that should be added to the HOWTO_RELEASE file.

--strk;