Add a RunProgram action

[cryptaliagy]

Quilla test files are just a collection of steps and minor configurations, which means that they can actually be reused by collecting the steps and ignoring most of the configurations. A RunProgram action would allow shared testing logic to be abstracted out either into its own Quilla test file (that can be run by Quilla), or possibly into a more barebones file that is configuration-neutral (i.e. that does not have the "targetBrowsers" and "path" fields, but would have a "steps" array and potentially a "definitions" object).

An example usecase would be having a "Login to portal" file that describes the steps and definitions required to log in to some application, which would then be used for other Quilla tests that require a user to be logged in to perform.