reorganize docs (mostly for the latex version)

ACKNOWLEDGEMENTS

INSTALL

doc/source/acknowledgements.rst

doc/source/authors.rst

doc/source/index.rst

doc/source/install.rst

doc/source/license.rst

doc/source/pre/acknowledgements.rst

doc/source/pre/authors.rst

doc/source/pre/index.rst

doc/source/pre/install.rst

doc/source/pre/license.rst

doc/source/pre/whatsnew/0.2.rst

doc/source/pre/whatsnew/1.0.rst

doc/source/pre/whatsnew/index.rst

doc/source/reference/index.rst

doc/source/reference/kwant.solvers.rst