Add support for updating user profile pic

[grahammcculloch]

Possibly make use of react-native-image-crop-picker.

Check out these PRs for details on the API endpoints to use to update the user profile picture:

https://github.com/appdevdesigns/appdev-opsportal/pull/315/files
https://github.com/appdevdesigns/appdev-core/pull/9/files