feat(common): Dictionary Self Learning (OBU)

### Is your feature request related to a problem? Please describe.

On behalf of user:

> Dear Keyman Developers,
>
> Please add Dictionary Self-Learning feature:
>
> Word count (frequency of use) from clients can be sent to server to update the dictionary. If initial dictionary had no words count at all (2nd column in lexical model was initially blank) then such input from users will be the only source of word count.

### Describe the solution you'd like

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### Describe alternatives you've considered

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### Related issues

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### Keyman apps

- [ ] Keyman for Android
- [ ] Keyman for iPhone and iPad
- [ ] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [ ] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

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### Operating system

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### Device

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### Keyboard name

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### Keyboard version

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### Additional context

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