[Feature request] Allow to nest same path Segment or Element in SegmentGroup (not consume it)

I would like to allow to use Segment or Element with same path as SegmentGroup - reconsider #32 or #36.
This would allow this class definition as:
```csharp
[EdiSegment, EdiPath("NAD")]
public class NAD
{
[EdiValue("X(3)", Path = "NAD/0/0")]
public string CodeQualifier { get; set; }

[EdiValue("X(35)", Path = "NAD/1/0")]
public string PartyIdentifier { get; set; }
}

[EdiSegmentGroup("NAD", "FII", "RFF", "CTA")]
public class SG2
{
public NAD NAD { get; set; }

public List RFFs { get; set; }
}
```
instead of:

```csharp
[EdiSegment, EdiPath("NAD")]
public class NAD
{
[EdiValue("X(3)", Path = "NAD/0/0")]
public string CodeQualifier { get; set; }

[EdiValue("X(35)", Path = "NAD/1/0")]
public string PartyIdentifier { get; set; }
}

[EdiSegmentGroup("NAD", "FII", "RFF", "CTA")]
public class SG2 : NAD
{
public List References { get; set; }
}
```
Both examples allow to reuse classes, but first one is clearer because it explicitly defines Segment property. It is also more intuitive for newcomers (i was bitten by it) than second form.

In general it could allow deeper type of "element" in outer one (like Segment or Element in SegmentGroup, but not SegmentGroup inside SegmentGroup).

This would change:

> Classes that are decorated with Segment, SegmentGroup, Message, Group or Interchange consume the segment that defines the contrainer and cannot be reused inside them.

I'm not sure if it would break compatibility, but it should not.

The issue names no files or tests. Start by tracing how EdiSegment and EdiSegmentGroup classes consume the segment defining their container, using the NAD/SG2 examples as the behavioral case; done means a same-path Segment or Element can be nested without consumption, while SegmentGroup nesting remains disallowed and compatibility is preserved.

Written by the indexing model from the issue text.