The graphical editor can now display and editor description files.
The library has been improved to provide more useful function.
The XML format has been slightly changed: only one soc is allowed per file
(this is was already de facto the case since <soc> was the root tag).
Also introduce a DTD to validate the files.
Change-Id: If70ba35b6dc0242bdb87411cf4baee9597798aac
