rename 'sdkversion' var to 'minSdkVersion' to avoid confusion
rename 'sdkversion' var to 'minSdkVersion' to avoid confusion

'sdkversion' is confusing when there is also 'targetSdkVersion' and
'maxSdkVersion'.

f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver