Recognise minimum prefix length

[Aerijo]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

Adds two settings for prefix length; one to use the value in autocomplete-plus, and another to optionally set a different one.

Alternate Designs

Could just always use the plus value, but users might want to set different values for snippets and literal text.

Benefits

More control over the menu

Possible Drawbacks

NA

Applicable Issues

Fixes #75
Fixes atom/autocomplete-plus#795

And possibly more

[Aerijo]

I still need to add tests

[aviatesk]

Any more update on this ?

[jherrman]

Hello, any ETA on when this will be merged? I still seem to be hitting the problem, even when I disable most of the autocomplete packages.

[muppetjones]

Going on two+ years. Does this need to be tagged for review?