Add props to summary statement

[prayaggordy]

May need to update both summary.lmabc and print.summary.lmabc. May need to implement print.summary.lmabc from scratch.

[prayaggordy]

Can probably just add it at the end; print.summary.lm returns invisible, so capture and add to it then cat.

[prayaggordy]

Add to summary return so people can $ and grab it.

[prayaggordy]

Add parameter show_props set to TRUE by default.

[prayaggordy]

In getConstraints() return a list of Con, pi_hat (or props if given) and update relevant function calls. Then return pi_hat with the rest of the information from lmabc.

[prayaggordy]

Also return the full design matrix in getConstraints().