Optimize the codebase

[rahulsain]

• [ ] Make few activities and more fragments
• [ ] Make fewer cloud calls and rely more on local dB
• [x] add the registered date when the user sign up
• [x] sorts group and notes by creation time
• [ ] remove random colors and color-specific notes color on dB (user can decide which color to choose from)
• [x] in group notes, one can see whose notes is this along with the name and photo
• [ ] save UI states