Temp url generation interface modification according to the aws and openstack providers

Implements:
- File#url
- Files#get_http_url
- Files#get_https_url
- Storage#get_object_http_url
- Storage#get_object_https_url

Refactors:
- Storage#generate_object_temp_url

Tests:
- requests/storage/object_tests.rb -> tests get_object_https_url, get_object_http_url

This is according to the discussion here: https://github.com/fog/fog/issues/2103