Document purpose of `apollo` property

[MartinMuzatko]

As a newcomer, the documentation leaves me behind confused and irritated.

• Why can't I just use the apollo client to query? Where to find it
• What is the design decision/benefit to use a property, not a $apollo.query method?
• How to re-evaluate the apollo property? How is it triggered?
• Is the apollo field executed only together with the created vue lifecycle hook? Sometime else?

This needs to be clearly documented and why this behavior is the default one.

[Akryum]

The goal is to write the queries in a declarative way. Everything is automatic. If you use a function for the variables, it will return automatically if they change.
Basically using apollo option is like data except it comes from your GraphQL API.

You can still do queries manually with this.$apollo but I don't recommend it.