Create a subfolder for ISA with common pieces

[kersten1]

I was playing around with includes and using a single source for multiple entries. Looks like you can include files, much the same way that we do with graphics. So what if we set up a subfolder called common or something like that and then create each piece as a separate file. Then it can be included in multiple locations. Only issue will be if it includes a header and an anchor name as then we would get dinged for having dup ids.

It would ALSO be excellent if we could pull from another repo, such as the glossary repo. Then we could pull in the definitions.