Flexible text parsing system

[Acclorite]

Why you want this feature to be implemented? Please describe.
When I think about uselessness, one thing explicitly comes to my mind—the text update and storing system (I think @shuvashish76 told me something similar). It has its pluses, for example, faster reader loading time, less dependency on files themselves, and maybe some more.

But what it really lacks is flexibility. I cannot easily change the whole reader, as that whole thing will need migration. What I want is a flexible solution that does not overcomplicate the UI and code—parsing files directly each time, without storing text in the app's storage. It will open the door to something bigger, such as Images (#69), Nested Chapters (#130), skip parsing in Browse, and more.

Describe the feature you'd like to be implemented
Simplify the code, remove text update, remove text storage. Directly parse text from the file each time user enters the Reader.