hide diam calc total field when only one trunk

fixes #655 on github.

Instead of having a readonly input field, the input field used for the inlineEditForm is now totally hidden. In addition, there is a input field underneath the worksheet that will show the total when multiple trunks are added.
Merge pull request #773 from steventlamb/bug/655/diameter_calculator_total

hide diam calc total field when only one trunk