replace ontology path with basepath and extension

instead of a full path to a file, use a basepath to specify the
ontology file and save the extension for easy access.
prevent fk constraint error on ontology version creation

prevent creation of ontology version before saving the ontology
which would trigger foreign key constraint violation.
add support for routing according to #172.
fix edit ontology link
speedup svn tests
fix test that was broken after change of path to basepath in ontology
speedup svn test in repository tests
change tests to use hash-based signature of git_repo.commits
change implementation to use hash-based signature of git_repo.commits
add constrained-commit-history test
make commits method on Repository more flexible by using hash-options
Merge branch 'develop' into git
add tests for passing a block in commits-iterator
add method for passing a block in commits-iterator
Merge branch 'git' of github.com:ontohub/ontohub into git
add possibility to pass a block to commits method
speedup multi-repository tests
add failure message to pending test
remove user from repository creation
add test for suspended_save_ontologies