Change color of focus and margin point

[droglenc]

Consider creating an option that uses something other than the same pch or col for the focus and the margin. This would make it easier to count the annuli.

Could set up a pch.fm= and col.fm= that could be set for the pch and col of the focus and margin. These could default to pch.show= and col.show= to maintain the current behavior. Consider dropping the points if showTransect=TRUE as the focus and margin are the ends of the transect.

[droglenc]

Handled differently than as described above. But will be addressed in v0.2.0.