Reorganizes the "schema" page on the website, and promotes much of the
permanode documentation to the website in its own page.

One of the goals here is to create an exhaustive list of camliTypes
and permanode attributes, and make it clear what they're used for.

Change-Id: I68a95fe5f870a9b25551b1e9c2eec805920d8931
localdisk: simplify directory locking.

Tries to fix https://code.google.com/p/camlistore/issues/detail?id=177

Change-Id: I2ea089437528d39ecdb8a3a3129e03ba11a76e67