Merge "Reword documentation"

### Types

Variables and properties are strongly typed, variables dynamically based on the

first assignment, and properties statically by the module type.  The supported

types are:

Variables and properties are strongly typed. Variables are dynamically typed

based on the first assignment, and properties are statically typed by the

module type.  The supported types are:

* Bool (`true` or `false`)

* Integers (`int`)

* Strings (`"string"`)

* Lists of strings (`["string1", "string2"]`)

* Maps (`{key1: "value1", key2: ["value2"]}`)

Maps may values of any type, including nested maps.  Lists and maps may have

trailing commas after the last value.

Maps may contain values of any type, including nested maps. Lists and maps may

have trailing commas after the last value.

Strings can contain double quotes using `\"`, for example `"cat \"a b\""`.

### Operators

Strings, lists of strings, and maps can be appended using the `+` operator.

Integers can be summed up using the `+` operator. Appending a map produces the

union of keys in both maps, appending the values of any keys that are present

in both maps.

The `+` operator:

* Sums integers.

* Concatenates strings and lists.

* Produces the union of maps.

Concatenating maps produces a map whose keys are the union of the given maps'

keys, and whose mapped values are the union of the given maps' corresponding

mapped values.

### Defaults modules

A defaults module can be used to repeat the same properties in multiple modules.

For example:

A `defaults` module can be used to repeat the same properties in multiple

modules. For example:

```

cc_defaults {