Roll back to v0.25, keeping the master branch usable.  New development is moved to the js-rewrite branch.

Reverts:
- "Early implementation of jwPlayer 5." / 765f76966b2efadf24a8781179d5c80b58140165.
- "Use jquery instead of document.getelementbyid calls." / cae3c7aa0d9e00c102a92706e4e9d0c01c53b109.
- "Work in progress: Rewrite to a simpler PHP backend." / 4d2d3a1a67d47b8765d979d6624588ec6763675c.
Sorry about the multiple reverts.  This makes the js-rewrite branch in sync with
the master branch, as well as keeping the latest development here.

Revert "Roll back to v0.25, keeping the master branch usable.  New development is moved to the js-rewrite branch."

This reverts commit 360d4d6a2891b4dc94aaac17c67275cde1b67c79.