Grouped notifications into one and show the notifications as a list

[kunall17]

This is expanding notifications not complete yet.
Wanted some suggestions if this can be made better

Expanded:

Default view: (the latest message is shown here) What would be the most appropriate content text here?

[smarx]

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[kunall17]

Updated

[borisyankov]

'New 4 messages' should be '4 new messages'.

If the message does not fit anyways, we should just say 'N new messages' without the 'from N conversations'.

Do we even want to group them though? How does it work in Slack & FB Messenger?

[kunall17]

Without grouping right now we are replacing the old notifications, hence loosing content
Slack and whatsapp both group messages in a similar way

[kunall17]

Fixed and added a commit to show the number of messages in the home screen
This is dependent on different launchers, library I used is popular and works well on my sony phone

[zulipbot]

Heads up @kunall17, we just merged some commits (latest: 8898fd8) that conflict with the changes your made in this pull request! You can review this repository's recent commits to see where the conflicts occur. Please rebase your feature branch against the upstream/master branch and resolve your pull request's merge conflicts accordingly.

[borisyankov]

Looks good to merge. Please rebase.

[kunall17]

Updated

[borisyankov]

Great. Thanks.