CDMI 3.0 - DSMD, add descriptive text about mobility scenarios

[dslik]

In the Data System Metadata section of the spec, we state" Data system metadata that is not supported by a CDMI server shall be preserved.". This means that if an object X is moved from server A to server B that does not support X, the data is retained even if it is not being applied, and if the object is then moved back to server A (or to server C that does support his metadata), the data system metadata resumes being applied.

Add additional text explaining this in detail.

[dslik]

Need to explain this with examples, e.g. use geographic location restrictions and give examples of where the destination system does not support the DSMD at all, where there is not overlapping support, where there is overlapping support, and talk about ahow policy decisions can be made based on this.