make clear about MAIC being different to other regression-based strategies

[n8thangreen]

the issue is with using the same formula notation. this is useful for reuse and ease of use.

• print message when using
• add explicitly to paper
• what else?

[n8thangreen]

what do other maic and propensity score packages do

syntax?
can we have a wrapper for alternative ways of specifying?
how to balance on not just means?
need to make clear what the generic regression formula means for maic, eg the trt interactino, em or pf used?