dialogs which allow editing of component properties. The button
is active when the table row cursor is on the DATASHEET field only.
When active, and your datasheet is a URI, then your default
browser will be launced to show that datasheet if it can find it.
This incentivizes use of http:// links for datasheets.
File "rules" has instructional text as comments near top.
2) Convert all text files in repo to LF line ending form.
Any checkout done with "rules" in play will convert the working
tree to native line ending, while keeping repo as LF line ending.