Documentation/basic_profiling.rst: convert to ReST markup

Convert it to ReST markup and add it to the user book:

- Add a title to the document;
- touch spaces/new lines to fix Sphinx format;
- use ``foo`` for commands;
- use quote blocks where needed;
- add it to the user book;

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>