Creates BestFitSequence model, with spec and migration

[#40210301]
Controller, helper, and view(s) for BestFitSequences

This makes the data model changes for [#40210301] available in the Hobo UI.
WIP on testing the BestFitSequence
Rails update to address vulnerability

ref: https://groups.google.com/forum/?fromgroups=#!topic/rubyonrails-security/61bkgvnSGTQ
Cucumber scenario for BestFitSequence

[#40210301] This passes up to copying the activity, but fails that last step.
Merge branch 'master' into line-of-best-fit
Updating generator to line_of_best_fit tag

[#40210301]
Making the dataset association work in Cucumber
Noting valid-activity requirements for BestFitSequences

Data sets of less than 6 points cause an error. Also, there needs to be a PredefinedGraphPane present (on the page, I assume) or the generator has problems. [#40210301]
Updating runtime to line-of-best-fit
Merge branch 'master' into line-of-best-fit
BestFitSequences data_sets need > 5 data points
Better data_set selection without the sleep call
Correcting from_hash method name in best_fit_sequence
Failing test to capture issues with from_hash
Had enough of two different spellings of "marshal"
A third spelling of "marshal" normalized
Changes to let SgMarshal respect relation class_names

Ouch. My head hurts.
We need the sleep in the data-set select. :(
Merge branch 'line-of-best-fit'

Conflicts:
	Gemfile.lock