Added corner detection feature

Added the ability to detect corners and highlight them.
Currently, the corners are only shown and you cannot move them and the app would not crop it automatically. The ability of the user to move the corners and to crop according to them will be added in future releases.
Also note that this and further releases will contain split APKs, i.e., there will be different APKs for different CPU architectures. So if you do not know what is the CPU architecture of your device, this article may help you.

Also if you are not a developer, it is recommended that you install a newer version (if available) or version-1.0.1 our first stable release.