Fixed a build error with aapt.exe by upgrading to latest version of build tools for 21
Fixed a build error with aapt.exe by upgrading to latest version of build tools for 21

willowcheng/Makerthings-android,MCherifiOSS/openhab.android,openhab/openhab.android,mrzottel/openhab.android,digitaldan/openhab.android,jvitkauskas/openhab.android,bodiroga/openhab.android,dominicdesu/openhab.android,willowcheng/Makerspace