Ensure that a generated form's page seeds are idempotent.

Fixes #2673
Merge pull request #2674 from refinery/fix-issue/2673

Ensure that a generated form's page seeds are idempotent.
Move url variable out to a less confusing placement.
When generating a form, only depend on a semantic version of refinerycms-settings.

This means we will get ~> 2.1.0 instead of ~> 2.1.2 so we won't
have to push a new refinerycms-settings gem for each version.
Documented changes since 2.1.2
Flash messages stored in session are html unsafe,

even if they were html_safe so we can't use html in welcome msg.
This is probably that should rails fix but meanwhile..
Separate pages_spec into separate files for each key function.
Merge pull request #2679 from awagener/split_pages_spec

Separate pages_spec into separate files for each key function.