Rearrange the docs repo folders and add CI config scritps for this repo

[jamesbeyond]

The changes had made to this repo:

1. removed all mbed-os.lib, only kept one mbed-os.lib in the root. (later when the sync up scripts split the project, it can add the same mbed-os.lib to each folder )
2. move each code the snippets to a 2-tier folder. the folder names following the convention of

 <Repo Root>/<Docs Topic>_<Category>/<Module Name>_<Example Name>/main.cpp

3. add CI configuration file enable circle CI runs on this project.
4. fixed some bug in the code

[jamesbeyond]

@AnotherButler, could you make a release to the repo as 5.14 before merging this PR?
Also once this PR merged, I can show you how to step by step add the CI. so you all the PR to this repo onward will getting some sort of complication test.

[AnotherButler]

Do you mean create a 5.14 branch?