Android AUTOFOCUS feature is now optional

This should allow apps using this plugin to be found in the Play Store on devices with no autofocus camera.

Support for 64-bit, additional UI options, and other fixes.

• Added support for the new drawSight option (see README).
• Now compiles and runs successfully on 64-bit iOS Simulator and 64-bit ARM (iOS).
• Fixed crashes on some Android devices.

Special thanks to @PaoloMessina for the code/fixes which made this release possible!

Added support for specifying front/back facing camera and setting flash mode

Closes #5

Added some text customisation parameters for Android

Fixes #6