added description of columns in sm_instance_index and sm_index.

minor text changes

updated ImageType description

check if include command works now

Moved section introducing indices of idc-index into README

Test to see if docs are build correctly

Docs: Added separate page for column description of indices and linked to it from README.

removed test

fixed link

removed doubled text

adapted toctree to generate column_descriptions.html

corrected toctree

another try

next try

a test

probably solved

added title and sections