separate sampler page for Interactives w/errors

[#45737301]

http://lab.dev.concord.org/doc/interactives/sampler/errors.html
distinguish errors in Interactive and Model

[#45737301]
wrap interactive definition path w/error in link

[#45737301]

To make diagnosing/reporting the problem easier.
removed overlay timer, fixed slider steps
simplified temperature selection using "good" values

I restricted the values that can be selected by the user to target
temperatures of 50, 500, 5000. Using these order of magnitude
changes in temp make qualitative changes in behavior clear.
text components, About: open links in new windows

[#46733573]

Also see earlier commit: fb6830f9
use markdown instead of html for about content

[#46733573]
Changed the server Gemfile, made ruby debugger and pry available in test env
Handle errors when updating interactives.

IM [#45693099]

Validate that an interactive's title is unique within a group and is not empty.
Validate that an interactive's path exists. Create a client side error
dialog to display interactive update errors.
Choose an interactive group when saving an interactive

IM [#45693055]
A user should be able to make copies of previously saved interactives.

IM [#45693489]
Disabled interactive save until after interactive has been updated

IM [#45694013]
Allow models that have images to served by web app

IM [#44394367]
Avoid trying to import interactives that are broken.

IM [#46684809]
Removed trailing whitespace from the last two commits
Makefile: import-interactives
Added missing interactive properties to rails model and presenter.

IM [#46210465]

The following interactive properties, (fontScale, template and exports), where not defined
in the backend, rails, model and presenter for interactives. This will require a reload of
the couchdb with `rake app:import:build_interactives`.
Interactives with a template property defined with an array are failing

IM [#46486373]
Add all the possible model attributes that can be defined in an interactive.

IM [#46561645]

An interactive can define a subset of the model attributes, e.g. modelOptions, onLoad, etc. The rails model,
interactive_model, contains all these model attributes. But, only the viewOptions where being returned by
the web/rails api.
Report device connection status in sensor applet experiment