Major rework of envelope address handling: a normalized version of the envelope addresses is maintained in the message context and message context is now also available during action execution.

Added registry for extension capabilities like the available notify methods and adjusted the enotify extension accordingly.

Made lda plugin properly refer to the main script as 'main script' and not the basename of the sieve file (which is of no interest to the user for the main script).

Added the concept of a script code header to list the extensions actually used by a script (was using all extensions listed in the binary).

RECOVERED FROM INCONSISTENCY: developed testsuite and binary dumping and fixed various small issues.

Further developed the include extension to compile included scripts in additional blocks of the binary.