Make Base IRI configurable

[matentzn]

This PR:

• Adds ability to properly configure base IRI tested here: https://gitlab.c-path.org/c-pathontology/critical-path-ontology.
  • Introducing OBOBASE variable, because the default for most of the imports should still be OBO. This can be overwritten, of course, by the user by setting mirror_from. (see makefile changes)
  • Various changes in template/_dynamic_files.jinja2, in particular about the PURLs for the imports.
• Removes redundant editors documentation
• Removes redundant sparql query template/src/sparql/class-count-by-prefix.sparql
• Removes a handful of redundant prefixes in sparql queries
• EDIT: Makes uribase_suffix configurable. This is used for assigning ontology IRIs to ontology internal files, like imports, and