Refactor files action of FilesController

Introduce service object RepositoryFile which
contains the logic of file and directory
retrieval on model level.

Introduce GitFile which contains logic of
file and directory retrieval on git/lib level.

Those classes separate the concerns of git/lib
and ontohub models way more.

Use InheritedResources for FilesController
and simplify files action (will be renamed later)
split history action off of files controller
fix remaining merge error
fix syntax error
code style
fix MethodMissing error
Fix retrieval of a user's repositories.

The repositories which a user is member of a team
with permissions were not selected.
use correct method to disable the name field
disable editing of repo name in controller
fix development state ("beta") label
Remove the possibility to edit an iri
Merge pull request #1032 from ontohub/741-IRI_should_not_be_editable

Remove the possibility to edit an iri
adding basepath to fullfill validations
Merge pull request #1033 from ontohub/fix_ontology_version_constraints

adding basepath to fullfill validations
deactivate presence of basepath validation
Merge pull request #1035 from ontohub/fix_validations_of_ontology_version

deactivate presence of basepath validation
Merge pull request #1031 from ontohub/fix_development_state_label

fix development state ("beta") label
Merge pull request #1027 from ontohub/fix_accessible_repositories

Fix retrieval of a user's repositories.
code style: surround arguments by parens
Merge pull request #1029 from ontohub/1025-form_field_disabled

1025 form field is disabled