Added rescue mode

Fixes #1126
Preparing update 2.0.0 Beta 1
Fixes error message text
Merge branch 'master' of github.com:WoltLab/WCF
Fixed frontend link in ACP menu
Merge branch 'master' of github.com:WoltLab/WCF
Fixed author comment of WCF.js
Fixed authors
Added system information
Merge branch 'master' of github.com:WoltLab/WCF
Fixed version number
Fixed border radius issues
Merge branch 'master' of github.com:WoltLab/WCF
Makes it possible to use template scripting in page menu items

This is helpful if the language item has different values based on option settings, e.g. if a certain part of the language item is only visible if a related option is enabled.
Merge branch 'master' of github.com:WoltLab/WCF into PCRE_UTF8