Add @DecimalMin and @DecimalMax for Hal+Forms Property Metadata

[talentedasian]

In the current Spring Hateoas, it is not possible to add a limit for decimal values. It would be useful for fields accepting decimal values.

@DecimalMin/@DecimalMax currently does not work and is only limited to having the @Min/@Max annotations.

[talentedasian]

Since Hal+Forms currently does not have specifications for decimals I suppose a decimal is still a "number" thus the Spring Hateoas team can just add support to @DecimalMin/@DecimalMax in the Min/Max Hal+Forms specification.

[talentedasian]

This feature would possibly require the min and max field properties to be changed from Long to either a BigDecimal or a Double.

[talentedasian]

Would be wonderful to also update the reference documentation.

[odrotbohm]

@talentedasian – Would you mind stopping to mess with the tickets and pull requests? I'm getting lost in all the notifications for this ticket. Please let us take care of that, thanks!

Reopening as there's pending work in an issue branch.