Make NEP validation errors more informative

[lock9]

Is your feature request related to a problem? Please describe. Neo Express is refusing to deploy our NEP-17 contracts, complaining that they are not NEP-17 compatible. There may be some problem on our code, but we have no idea where it is. There are multiple validations but only a single error message.

Describe the solution you'd like Neo Express should inform which field is failing validation.

Additional context If possible, the user should be informed of all errors at once instead of returning just the first error that is found.

[cschuchardt88]

You can bypass by using --force

[lock9]

I don't want to bypass it. I want to know what the problem is.

[cschuchardt88]

@chenzhitong you want to take this one?