Define a serialization format

[dumoulin]

In 0.2, serialization was accomplished with XStream and was reduced to serialize to top-container object.

The file format aims to store a mole, a workflow or a task, and could be designed as an archive with a set of files. One file for each of them:

• a task
• a workflow (capsule + transition)
• a plugin archive (including data structures)
• a file resource
• a mole (only one mole per archive)

Dependencies between two elements in different files are wroten using element's hash.