Roll API minimum level to 11

Pros: We get more features, like easier asynchronous task execution
Cons: We lose ~40% of Android devices
Refactor API access into WalkingArchiveApi class

[#47184969]
Migrate SearchActivity to new WalkingArchiveApi

[Fixes #47184969]
Merge branch 'api_refactor'

Conflicts:
	src/org/walkingarchive/app/SearchActivity.java