add Model

add Chain
simplify Context
optimize Actor
change license from MIT to Apache-2.0

 - compatible with gcc4.8 compiler.

   - add cpu affinity inorder to support cpu binding.
   - add dynamic library unload.

add configuration management and test passing with Nebcli.

 - NebulaBeacon adds node status information query, registration cent…

…er leader-fllower arbitration.

   - NebulaInterface adds hello demo.

ipv6 support

https server and client test passing

distributed log service test passing. add https support. add keep ali…

…ve settings to http channel. replace repeated http headers with proto3 map. provides a symmetric encryption key setup interface for channel. bug fix.

test passing with an data analysis application named Nebio

rewrite nebula with c++14 had been completed, both cluster test and h…

…ttp request test had been passed.

first release version