5. check how SPM defines contrasts

[carmzh]

Ideal workflow:

1. User define ANOVA: mod <- ez_aov()
2. Define list of within contrast and/or between contrast
3. State method = "post-hoc"

Issue:
check SPM contrast function

Function workflow:

• {does the user want between, within, or between by within (multiply all between x within contrast vectors), or pairwise} to scale? or not to scale?
• check contrast vector are correct length using df from the model (Issue 3c: write function for this)
• create contrast() tables as required
• compute critical constants (cc)
• CIS