Gallery improvements

[sudoDeznit]

• Extracted useful functions and code from forked library code
• moved image fetching to redux -- for fetching on app load
• moved gallery navigation to react-navigation
• added gallery permission request screen
• added option to open settings if request is denied earlier or else request for permission
• added Appstate listner on gallery permission screen to check for permission change on app focus

NOTE

• I have not deleted the old code of gallery. kept that for reference, can be removed once the PR is reviewed and tested