SCA2: now with file support

I made a few changes to the Sound Change Applier.

First, files should be supported. That is, you can now download your work to a file, and upload it back into SCA².  You can include the input lexicon or not.

(I use the download attribute on browsers that support it, and another method for Explorer and Edge.  Hopefully it’ll work on your browser.)

Second, you can now have intermediate results. E.g. you could generate Old Ibero-Romance and then Portuguese with the same sound changes.  (Basically: add the special rule -* at the appropriate place in your sound changes. You can add a descriptive name after it.)

See the help file for details on both changes.