[WIP] Check system date when starting packaged Marketplace (bug 1019122)

If the device clock is too far behind the user will get a certificate error, so let's display our own error message instead.

WIP, need translations first, the translations for the error messages generated by yulelog package are directly hardcoded into the package main.js file :(
Yeah. I noticed the offline error message isn't even in the locale/ .po files, so how were the translations gathered ? Should I just ask someone (Wil?) to get translators to do it for me ? Or should I try to integrate these translations properly with the rest ?