This can be handy instead of having to move over the character with
arrow keys and such.

@bindir@ was not getting fully expanded, instead it was expanding to
${exec_dir}. This forces it using a sed expansion.

This should fix executing Builder from the icon in gnome-shell.

We might also want to index on all of the directory names, so we can open
the directories as well. Needs UX/DX work though.

This allows you to have a GtkScrolledWindow that will be at least
min_content_height/min_content_width big, but grow to no more than
max_content_height/max_content_height big.

Also, try not to be completely braindead when building the widgets with
regards to string copying. It's not great, but it's a step forward.