Conditionals: Allow access to pipeline resources

[dibyom]

Expected Behavior

Condition containers should have access to the resources themselves e.g a fileExists condition to check if a file exists in a git repo.

Additional Info

The resources that the condition needs have to be explicitly specified so that we do not needlessly initialize all resources for each condition check. Based on design in #27

ref: #1137

[dibyom]

/assign