Implemented the adjustable sleep timer feature as requested. Updated the settings storage to include refresh interval and default folder preferences. Modified the state file version to accommodate new fields for last browsed folder.
- Added new `useCoverArtPicker` setting to CrossPointSettings.
- Updated saveToFile and loadFromFile methods to handle the new setting.
- Modified ReaderActivity to use CoverArtPickerActivity if enabled.
- Adjusted settings count in SettingsActivity.
## Summary
* Consolidate chapter page data into single file
* Header structure of the file stays the same, following the page count,
we now put a LUT offset
* The page data is all then appended to this file
* Finally the LUT is appended to the end of the file, and the page count
is updated
* This will also significantly improve the duration of cache cleanup
which takes a while to scan the directory and cleanup content
* Remove page file version as it's all tied up into the section file now
* Bumped section file version to 7
* Moved section content into sub directory
* Updated docs
## Additional Context
* Benchmarks:
* Generating 74 pages of content from a chapter in Jade Legacy took:
* master: 6,229ms
* this PR: 1,305ms
* Speedup of 79%
* Generating 207 pages of content from Livesuit book:
* With progress bar UI updates:
* master: 24,250ms
* this PR: 8,063ms
* Speedup of 67%
* Without progress bar UI updates:
* master: 13,055ms
* this PR: 3,600ms
* Speedup of 72%
