Give more information when the SDK cannot load because of missing files

[codeanticode]

trafficstars

Right now, the mode simply says that the Android SDK was found but there are some missing files, which makes hard to know what exactly is missing, as discussed here.

[rupak0577]

The error was probably because the user's preference file contained the older SDK version but the required files were not present in the SDK location. The mode prefers the version set in the preferences as can be seen here.