Add support for the group element

[rjordakiev]

Working on a change that allows respecting the order imposed by xs:sequence in schema, which is an existing issue (#1267).

Respecting the xs:group element is also of importance since there are specific cases when the sequence appears as a child of the group.

[rjordakiev]

Is there any intrinsic reason that the group element is commented out and parsed as UnexpectedElement that I may be messing or it simply is obsolete for the current implementation?

[w666]

Could you please add some tests for this? it would help to understand the changes and lock down the implementation. Thanks.

[smokhov]

Is there any intrinsic reason that the group element is commented out and parsed as UnexpectedElement that I may be messing or it simply is obsolete for the current implementation?

IMO, it's history the OG devs would know. Whatever was the reason, we don't need to dwell on it, and push the project forward, so thank you for your contribution.

I see in your fork you also did commit an implementation of the sequence ordering; that other branch has tests. Do they cover this group element as well? if so, then why not include it into the PR as well? It seems from your implementation group element is required to enable proper sequence ordering anyway.

[smokhov]

Could you also explain this comment in relationship to:

node-soap/src/wsdl/elements.ts

Line 207 in 012457e

public $minOccurs?: string;

I am curious.