Make the following changes to doxyfile_options:
-Change CASE_SENSE_NAMES so names of files generated match mbed-os docs
-Change DISABLE_INDEX so navigation bar shows
-Change CLASS_DIAGRAMS so inheritance diagram gets generated
-Change USE_MDFILE_AS_MAINPAGE and add DOXYGEN_FRONTPAGE.md to
    FILE_PATTERNS so the correct main page is found and used
-Remove DEVICE_ETH from PREDEFINED since this is no longer relevent
-Change GENERATE_XML and XML_OUTPUT so no xml is generated
-Change SEARCHENGINE to match the docs

Make the following changes in doxygen_options.json:
-Add all non-default values in doxyfile_options to the json
-Break json into 3 groups
    1. Values that are the same as doxyfile_options
    2. Values that must be different from doxyfile_options
    3. Values the are overriden by the docs builder
-Make the doxyegn search directory "INPUT" start in mbed-os rather
    than one level above mbed-os.

Finally, rename the BLE doxygen front page so it is not confused with
the mbed-os front page.