uniform CHANGES format for version 0.5.5
fix PL-PGSQL error when restoring a database backup

When restoring a backup on Postgresql 9.x following error was occurring:
ERROR: An error occured while calling pg_restore: pg_restore: [archiver (db)]
Error while PROCESSING TOC:
pg_restore: [archiver (db)] Error from TOC entry 199; 3079 11733 EXTENSION
plpgsql
pg_restore: [archiver (db)] could not execute query: ERROR:  syntax error at or
near "EXTENSION"
update CHANGES for 0.5.6
update TODO
Merge changes for 0.5.6 from branch 'develop'
set m2ee module version to 0.5.6