Dropdown for account switching
Use player face in accounts dropdown, grab all valid account skins on startup
Merge remote-tracking branch 'upstream/feature_yggdrasil' into develop
Add support for "no default account"
Could reach end of rulesFromJsonV4 method without returning a QList

It was possible for execution to reach the end of the rulesFromJsonV4
method without returning. This was causing a crash on OS X when parsing
rules inside an instance.
Merge https://github.com/Drayshak/MultiMC5 into develop
Merge https://github.com/brainiac744/MultiMC5 into develop