Add passive gesture data gathering

[Helium314]

@theeclecticdyslexic it's mostly working and done.
Passive gathering will be used whenever isPassiveGatheringUsed returns true, the same result also determines whether the indicator icon is shown. Indicator is a red icon at bottom left, which is a ring or a circle, depending on whether data is cached.
Cache is written when closing the keyboard or switching input fields (and maybe on some more occasions).
Gathering is stopped and cache is cleared when entering incognito mode, or disabling passive gathering via the toolbar key. Toolbar key is available only after having passive gathering enabled at least once. Long-press disables gathering for 5 min.

There are settings to decide in which apps passive gathering is enabled, and which words are excluded.
The review screen allows filtering, sorting, selecting, deleting and sharing data.

What's missing / could use improvement:

• icon choice / color / placement
• not properly working in combination with inline emoji search
• I don't like the 3 switch layout in review screen
• not sure what info to show when tapping on a word in review screen
• info text about passive gathering is completely missing (planned contents in a todo in PassiveGatheringSettings
• testing
• some more todos