This reverts commit e528b9f5.

I was originally convinced by the argumentation (quote always in same place)
but testing this out for a while really seems to break 'last correct' for me.

I use that way more frequently that quote

- Add setting to prevent screenshots
- Enforce using FLAG_SECURE in onResume for each activity

Rewrite QuoteHelper to integrate French quotes logics. Also reallow QuoteChars not followed by whitespace as indicated in XEP-0393.

QUOTING_MAX_DEPTH=1 for transitory compatibility with older versions. QUOTE_MAX_DEPTH=7 for performance testing and hiding of a rerendering bug occuring when two adjacent messages are merged.

since 0 is a valid file size we should use null to indicate absence