Integrate Makefile to build with make

[aregtech]

Similar to CMake and MSBuild, there should be integrated Makefile in the root or areg-sdk-demo to build with make.
The logic to build withmake should be the same:

1. set the root folder of areg-sdk
2. specify the output folder for binaries
3. build projects in demo
4. by default, exclude building the examples of areg-sdk, as well as the possibility to include examples in the build.

I would assign this issue to anyone who is interested to implement this small task.
As an example, see how it is done for CMake.