plugin dep install rate should be more configurable

Today custom overlays (plugins by convention) run `npm install` at a rate of once a day - this means if you're developing an overlay, or have an overlay with loose semver requirements (and a downstream package updates) the only way to get more frequent updates is to delete [the lockfile](https://github.com/bengreenier/overlayed/blob/master/src/app/helpers/PluginGrid.tsx#L17) manually.

Start with src/app/helpers/PluginGrid.tsx, especially the lockfile handling and the daily npm install behavior described in the issue. Trace how custom overlays are discovered and installed, then make the install rate configurable and verify that developers no longer need to delete the lockfile manually to receive updates.

Written by the indexing model from the issue text.