clarify no adding members to existing quests

Should hopefully cut back on the number of newer players starting a quest and thinking they can add other folks
improve(i18n): move translations to their own module, use i18n from habitrpg-shared, @djuretic i have remove the tests because the code is now handled in habitrpg-shared, we may add them back there
improve(i18n): use strings for gear items and potion
refactor(i18n): use strings for content
refactor(i18n): refactor user language detection, add to api methods
refactor(i18n): add language detection to new user
refactor(i18n): add comments
refactor(i18n): refactor & fix
fix(i18n): typo
fix(i18n)
fix(i18n): use habitrpg-shared branch for bower
fix(i18n): use strings
fix(i18n): better strings for items
fix(i18n): use strings
fix(i18n): use right strings
fix(i18n): group name
fix(i18n): group name
fix(i18n): user creation does not override preferences
fix(i18n): spaces around string
refactor(tour): start using custom template