Re-designed and Linked Details Page

[PragatiVerma18]

Fixes #40

• Re-designed the Details Page so that UI remains consistent
• Implemented Nested Navigation( Stack Navigation inside Tab Navigation)
• Also added a functional back button to navigate back to the previous screen
• Refactored App.js and separated navigation components into src\navigation
• Added custom header to all screens such that it's easy to keep track
• Made all cards on Home and Dashboard touchable so as they open up the Detail view

See the Demo Video below for further info:

https://user-images.githubusercontent.com/42115530/102712763-7ef91b80-42e9-11eb-87a9-95938bb2b9fd.mp4