This allows for PHPDoc-style types to be used in MainConfigSchema,
and adds aliases for the 'object' and 'array' types, to avoid confusion.
The type 'map' can now be used for associative arrays, it will be
represented as 'object' in JSON Schema. Similarly, 'list' can be used to
refer to sequential arrays, it will be represented as 'array' in JSON schema.
In addition, the basic PHP types are mapped to their JSON counterparts,
including support for nullable types. For example:
"?map" will become [ "object", "null" ];
"float|false" will become [ "number", "boolean" ];
Change-Id: I89617d06afd1e97ee1bc9bc49b6c77bed7bd50d9
123f4d8dfc