Developer changes in 1.4.

Hello!

We've just released Silva 1.4, and have created a short list of known
API breakage for developers. The following points are known issues for
using extensions on 1.4 that are written for Silva 1.3, there may be
more problems, please see HISTORY.txt as well.

   * Added hide_from_toc to metadata set, which replaces some old hacks.
     Extension writers can clean up code that uses the old
     'hide_from_tocs' attribute.

   * Refactoring of object lookup - the old object lookup screens have
     been replaced with a new one. This change will break old extensions.

We hope you will enjoy Silva 1.4, if you have questions or notice more
changes in API that can cause problems for older extensions, please let
us know.

Cheers,

Guido