Create a new section in the meta-data called "hints" where users can
provide hints about a given property. The most basic use case for now
is to provide a list of values that a property can have. Each value may
have a description.
This sample JSON provides a basic example for a property called `foo.mode`
that exposes 3 values: "auto", "basic" and "advanced".
```
"hints": [
{
"id": "foo.mode",
"values": [
{
"value": "auto",
"description": "Some smart description."
},
{
"name": "basic"
},
{
"name": "advanced"
}
]
}
]
```
This information can be read by tools (such as IDE) and offer an
auto-completion with the list of values.
Closes gh-2054
bc9321734f