Add version check page

[MyXoToD]

Maxdown needs a page to check the current version. This is useless while using the app via web but it's very important for using it "offline". The page would should the current version installed and the most recent version available.

[MyXoToD]

It's some kind of implemented now. The manage/settings section show the current version. Next thing would be: Check for latest version available.