Adds `pluginVersion` to saved options and Fixes failing test.
Adds `pluginVersion` to OptionsStore.

* PluginMeta gets the `needsUpgrade` helper that can autodetect if the
  plugin needs to be upgraded.
* Any required schema migration should be done behind `needsUpgrade`.
Merges branch 'feature/add-plugin-version-to-options-store' into develop
Updates changelog.