FIXED: offline mode fixes

 * fixed: Splash screen not closing
 * fixed: AuthlibDLWorker not catching all exceptions caused by network
FIXED: more offline derps

 * Save userdata after succesfull login
 * Remove unneeded logging
ADDED: automacally convert logindata
 * Automatically convert logindata to new format
 * Advice user to ignore decrypt errors while converting
Merge pull request #727 from jikuja/fix_logindata_convert

ADDED: automacally convert logindata