[doc][design] Target use cases

[at15]

What is Xephon-S designed for

Targets

• small edge devices (like sqlite, realmdb)
• single node, in (main?) memory
• distributed (like Cassandra) but maybe there is no requirement for consistency

Run Machine learning in-place

• https://github.com/tiny-dnn/tiny-dnn Header only C++11, could be used for IoT devices (mxnet was all I think about before run into this when goolge ArrayFire mxnet)

Future plan (a.k.a don't implement in current plan)

• multi tenant