Support full JSON Schema validation

[cyrilletuzi]

Only a subset of JSON Schema is used to validate the data in this lib. Just follow the provided JSONSchema interface.

In version 5 of this lib, you can only use:

• type
• properties and required
• items
• required

Since version 6 of this lib, you can use:

New types:

• enum
• const

Validation of numbers:

• multipleOf
• maximum
• exclusiveMaximum
• minimum
• exclusiveMinimum

Validation of strings:

• maxLength
• minLength
• pattern

Validation of arrays:

• maxItems
• minItems
• uniqueItems

The following ones won't be included because the role of the validation feature in this lib is to check the data against corruption, so validation should be more strict:

• additionalItems
• additionalProperties
• propertyNames
• maxProperties
• minProperties
• patternProperties
• not
• contains
• allOf
• anyOf
• oneOf
• array for type