Add the first version of tinyms serving module

[leonwanghui]

Please NOTICE that this is the first verison of TinyMS Serving module implementation, and a lot of changes and design proposal would be added later.

What have we done?

These jobs below have be targeted by this PR:

• Develop client and server module beside serving module, and expose start, shutdown and predict method to the public
• Design a simple CS communication mechanism by using requests and flask package
• Design the intial JSON payload when predicting an image from the serving client

Next step

For the whole serving framework, we still have a lot of work to be finished:

• Move servable definition from client to server module, which means users don't have to specify the detailed information of servable when predicting an image
• We need to design a product-ready CS communication mechanism, possibily relied on openapi-generator
• Some unit tests and e2e tests would be added later

[lyd911]

lgtm

[huxiaoman7]

lgtm