[#71] Remove corrupted APKs

* If the download fails, clean up APK directory
* Display friendly error
* Add string resources
[#71] Update function name for a more meaningful one

* Use 200 status code constant
Merge branch 'hotfix/apkupgrade' into develop
[#73] minor spelling fix on label
[#70] Increase version number after hotfix
Merge branch 'develop'