added a mechanism to pass in the authorization header separately, so that we can deal with OAuth, etc.

From http://commons.wikimedia.org/wiki/File:Dialog-accept.svg
The work is in the public domain.

Bundled plugins should be laid down as *.jpi, with proper measure to
migrate existing bits.

Document parts of FilePath.

FilePath was a little lacking in documentation, this documents getRemote,
createTempFile, createTextTempFile and createTempDir.