filled in MDS match API
Added the entity Sharing system

This abstract interface covers remote copies
for most meshes, a mix of remote copies and matches
for matched meshes, and possible user-defined
scenarios, such as custom ownership rules.

It is used in field synchronization and accumulation
as well as owned entity numbering, numbering synchronization,
etc.
Merge branch 'master' of https://github.com/SCOREC/core