Renamed `enable_lfs` to `lfs_enabled` for the Project field, and related fixes.

app/assets/stylesheets/pages/projects.scss

app/controllers/projects_controller.rb

app/helpers/projects_helper.rb

app/models/project.rb

app/views/admin/projects/show.html.haml

app/views/projects/edit.html.haml

db/migrate/20160823213309_add_lfs_enabled_to_projects.rb

db/schema.rb

doc/api/projects.md

doc/workflow/project_features.md

lib/api/entities.rb

lib/api/projects.rb

spec/requests/lfs_http_spec.rb