Some minor refactoring
Fix link on 404 page.

TODO this 404 text should be internationalised.
Improve i18n workflow

* remove generated files from version control
* generate i18n-abide required files from po during postinstall

Closes #388
mkdir before compile-json
[#389] Don’t warn if i18n/ exists.
[#389] Clarify translation instruction a tiny bit
[#308] Add recent changes page