Update 1-basic-concepts.rst. Add cross-link labels

Allow to cross-link to basic-concepts chapter using :ref:`title <basic-concepts>` .
Allow to cross-link to inline-notation-vs-tag-based-notation sidebar box using e.g. :ref:`inline-notation-vs-tag-based-notation` (or providing a title see above).
Fix missing colon.
Fix missing colon.
Merge pull request #11 from faerietree/patch-5

Update 1-basic-concepts.rst. Add cross-link labels