First Doxygen output

[metc]

@rgrover added Doxygen support in commits 04d10f6 and f72edf4.
This is great! IMO, it is a must have for an API 😏

I refactored all Doxygen stuff to a specific folder (to keep some consistency, I did the same as mbedtls) . I added a Makefile to generate the doc automatically and fix some typos (especially wrong Markdown syntax).

This is the very first Doxygen output and the documentation is not well formatted yet. A lot of polishing is needed... I am not native English speaker, so I cannot correct the doc or add Doxygen pages.

What we can do is publishing automatically the Doxygen documentation (for release versions) to gh-page so the doc is available online instantaneously (here is an example - https://tls.mbed.org/api/). I can do this job, please let me know if you are interested...

[ciarmcom]

Automatic CI verification build not done, please verify manually.

[metc]

What is wrong with Mr. mbed Jenkins CI @ciarmcom ?

[rgrover]

thanks so much for submitting these changes. I've merged a conservative version of your proposal into develop. Doxygen related files are still under flux. We'll soon merge develop into master and publish doxygen docs. (ref @iriark01)

[metc]

Thanks @rgrover for merging this PR. According to fa755f1, you are not interested in the separated folder, Makefile or a Travis CI setup ?
Should the Doxygen intro page be merge with the README file ?
Can you also explain me what is wrong with the Automatic CI ?

[rgrover]

Chris (ref @metc), we're aiming to host documentation using docs.mbed.com. Integration with this system is currently under progress. We'll be releasing something shortly.

[metc]

Great, makes sense. Please let me know if I can help.

[rgrover]

You can help by continuing to submit improvements to the documentation.

[rgrover]

@metc : https://docs.mbed.com/docs/ble-api/en/latest/api/index.html

[metc]

Thanks @rgrover Need some polishing but this is a good start 🎶 See #120
Do you have to publish the Doxygen output manually or is the process automated ?

[rgrover]

@metc: presently, it is a manual process triggered from the 'master' branch. So it would take some time before changes make it to the user-visible documentation; but we can trigger a rebuild if there are significant improvements to docs. @iriark01