Implement the tree file structure iteration for the fetching of images

[rohanagarwal94]

Actual Behaviour

The images are being fed from the MediaStore class. Even the caching of the images are repetitive at various places in the codebase.

Expected Behaviour

The users will be shown only the images which he wants to see. The caching of the images should be made into separate class rather than cursor over MediaStore each and every time. Additionally, the max file size in the settings will also be implemented. This is created in reference to #285 . It will speed up the transition to image picker activity too.

Would you like to work on the issue?

Yes, I would like to work on it.