Fixed various JS-API errors
Fixed various JS-API errors

Form element values were included in POST-requests, even if they were not checked (violating intended behavior). Furthermore inner template content is now properly purged if the next step would evaluate as 'success'.

cashcat/WCF-1,WoltLab/WCF,Morik/WCF,Morik/WCF,PhrozenByte/WCF2,joshuaruesweg/WCF,Cyperghost/WCF,WoltLab/WCF,joshuaruesweg/WCF,NBZ4live/WCF,0xLeon/WCF,Cyperghost/WCF,MenesesEvandro/WCF,MeinAccount/WCF,WoltLab/WCF,cashcat/WCF-1,MeinAccount/WCF,Morik/WCF,SoftCreatR/WCF,0xLeon/WCF,SoftCreatR/WCF,ramiusGitHub/WCF,joshuaruesweg/WCF,Morik/WCF,PhrozenByte/WCF2,0xLeon/WCF,Cyperghost/WCF,Cyperghost/WCF,MenesesEvandro/WCF,NBZ4live/WCF,SoftCreatR/WCF,Cyperghost/WCF,WoltLab/WCF,ramiusGitHub/WCF,SoftCreatR/WCF