Add gettext-based translations

[ChristophWurst]

Fixes #97

Todo

• Test with a real app
• Test placeholder replacement (not sure if %s or {placeholder} should be used
• Set up https://docs.transifex.com/transifex-github-integrations/github-tx-ui

[ChristophWurst]

Test placeholder replacement (not sure if %s or {placeholder} should be used

We'll eventually need this for every package that is translated, so I added this functionality to the l10n package: nextcloud-libraries/nextcloud-l10n#88

[nickvergessen]

Test placeholder replacement (not sure if %s or {placeholder} should be used

JS uses {} + %n
PHP uses %s, %1$s + %n

Ref nextcloud/documentation#1827

[ChristophWurst]

JS uses {} + %n

Done via nextcloud-libraries/nextcloud-l10n#88. Please have a look :)

[rullzer]

Lets merge this so we can setup transifex push/pull