_maxId should be removed, $loki should be able recycled.

[lygstate]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/LokiJS-Forge/LokiDB/blob/master/CONTRIBUTING.md#question

Current behavior

Expected behavior

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

LokiDB version: X.Y.Z


Browser/Node version: Browser X.Y.Z.

Others: