Add offline support for all the teller functionalities using Couchbase and sync-gateway

[varsvat]

Fixes #FINCN-328

This PR has been created on top of PR #189 and extends offline-first support for Teller functionalities like Creating, editing and updating Tellers and also the support or task management features have been implemented, all with the Couchbase only interaction.

Couchbase-server :

Sync-gateway :

https://user-images.githubusercontent.com/53621853/124877718-f7ef6480-dfe8-11eb-8841-2fa140137238.mp4

https://user-images.githubusercontent.com/53621853/124877806-12294280-dfe9-11eb-932b-24073f6d94e0.mp4

https://user-images.githubusercontent.com/53621853/124878041-4a308580-dfe9-11eb-93f4-1124ff89842e.mp4

Please Add a Summary of what changes you have made and if possible provide links.(Optional)

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[varsvat]

@jawidMuhammadi Please review this PR whenever you get time.

[jawidMuhammadi]

@varsvat Please squash commits into one

[varsvat]

@varsvat Please squash commits into one

shall I keep the couchbase commit separate or not? Also, have you reviewed the changes @jawidMuhammadi ?

[varsvat]

I have squashed the commits. Now we should be ready to merge this PR :smile: