Introduce reference tracking in Cache
Introduce reference tracking in Cache

Any links to a record will be stored on that record's `refs` property, keyed by the full path of the link.

These references are automatically tracked in the Cache as records and links are added and removed.

greyhwndz/orbit.js,lytbulb/orbit.js,ProlificLab/orbit.js,opsb/orbit.js,lytbulb/orbit-firebase,SmuliS/orbit.js,opsb/orbit-firebase,opsb/orbit.js,opsb/orbit-firebase,rollokb/orbit.js,lytbulb/orbit.js,jpvanhal/orbit-core,orbitjs/orbit-core,jpvanhal/orbit.js,beni55/orbit.js,jpvanhal/orbit.js,lytbulb/orbit-firebase,ProlificLab/orbit.js,jpvanhal/orbit-core,opsb/orbit-firebase,rollokb/orbit.js,greyhwndz/orbit.js,beni55/orbit.js,gnarf/orbit.js,SmuliS/orbit.js,lytbulb/orbit-firebase,opsb/orbit-firebase,orbitjs/orbit.js,orbitjs/orbit.js