adding executable scripts

- users can now write specific use scripts for use with the app. The
scripts can access any variables the one-liners can, but get the added
benefit of executing on a background thread.
- added a first draft of an "exploud" script to make the game stop
yelling at you. Cannot test it until we can save...
parser loading bugfix

- there was a resource leak when loading a new parser - not all the
previous elements got recycled correctly.
- there was a jump error where loading a different parser on the same
file jumped back to the top instead of keeping the current location.