Ticket [7665c3532c]. Matching the empty string, i.e. epsilon.

Extended the Literal command in the AST traversal part of the PEG
importer to recognize the empty string and generate the proper PE
(i.e. epsilon).

Extended the Convert command of the PEG exporter to properly convert
epsilon into an empty string.

Extended testsuite.
(Not fully tested yet)
Fix all issues with the extended tests. I.e. replace various placeholder data with the real thing.
Bumped versions of the modified packages. Updated ChangeLog.
Merged the pt epsilon bugfix.