Add Image_question to the activty_runtime_api
blob.rb: Add mimetype,  file_extension, checksum

Learner.rb: Add assocation to lightweight_blobs <=> blobs
Also: add methods to pull content from URL, generate checksum
&related tests.
ProcessExternalActivityDataJob -- adding image question answers.

proceess_external_activity_data_job.rb: support  image_question
&update spec / features
blob.rc typo: leightweight_learner ➙ lightweight_learner
move webmock/rspec require to spec_helper.
maven_jnlp_server_spec.rb : Mock web request to jnlp server
activity_runtime_api_spec.rb :  Fix broken test, external_id is a string
00_core_extensions.rb: Ensure that Object#display_name works for Objects

Used to only work for ActiveModel classes.
Fix typo in spec.
blob_spec.rb : Fix typo in text of assertion.
First pass of exposing an endpoint to publish a Lara sequence.
Ignore new-style ruby version and gem set files
WIP: specs for the new sequence-aware publish API
WIP on publishing sequences (mostly tests)
Functioning spec for activity_runtime_api
activity_runtime_api factors out activity creation

This pulls out the actual creation of activities and child components from the hash into its own method, so it can be used both by publish_activity and publish_sequence.
API passes unit testing for publishing sequences
WIP on publishing sequences: glitches testing updates

[#53637857]

https://www.pivotaltracker.com/story/show/53637857
Fixes test setup for sequence updating via API.

This should finish support for publishing and updating sequences using the same endpoint as the existing activity-publishing API, once it's checked against the client (LARA). [#53637857]

https://www.pivotaltracker.com/story/show/53637857
Fixing scope of @existing_sequence creation

[#53637857] Getting the tests right.

https://www.pivotaltracker.com/story/show/53637857