Migrate to github, update accordingly:

* Patch-Version bump (v0.3.1)
* Reformat docs more sanely.
* CHANGES.txt, COPYING.txt, TODO.txt: Move into base-dir.
* CHANGES.txt: Cleanup file format, order.
* exportvid.cmd: Update copyright years.
* README.txt: Add summary info & copyright, "features" from SF, reformat.
* .gitignore: Add empty.