templates/about: Use btn-group for social buttons
Merge pull request #102 from Turbo87/i18n

Updated translations from launchpad
import_srtm: Use preprocessed TIF files from the download server
Merge pull request #96 from Turbo87/btn-group

templates/about: Use btn-group for social buttons
Merge pull request #103 from Turbo87/srtm

import_srtm: Use preprocessed TIF files from the download server
i18n: Updated Polish translation