Error Message Localisation

[Azareal]

A lot of the error messages aren't localised, although they're hopefully things the users won't be running into one a too frequent basis, we might want to localise these sooner or later though, so that people who don't speak English can understand the errors better.

[Azareal]

The really common error pages have been internationalised, so people can make language packs for those to target their native language, I might throw one together myself, we will see. I've also internationalised the alerts builder, so those are no longer hard-coded phrases.