First step for #3692, Add support for new opencaching nodes

- Extend key handling for the new sites
fix JavaDoc
Merge remote-tracking branch 'upstream/release'
Version code
Manual alignment version code between branches

My fault
Manual alignment of branches

Don't say a word :(
Merge branch 'release' into upstream
Merge branch 'release' into upstream
Merge branch 'release' into upstream
Merge branch 'release' into upstream
refactoring: remove redundant variable
Merge branch 'release' into upstream
avoid lint error in test
Restrict this version to Android >= 2.3
Partially revert < 2.3 compatibility mode

This reverts part of 46675dfdcb4c7b511b4c35e4a2242e47d4678fd4. However,
since this commit did some cleanup and simplifications, we keep them.
Remove now useless changes to RxJava
crowdin: New translations
Update minSdkVersion in tests
Remove compatibility with API < 5
Remove compatibility with API < 8