DxBuilder: Only determine default values *after* object has been added to container.

This solves an issue with IntID generation for objects. I have no idea why this
works, but it seems to resolve our current test failures.
Merge pull request #28 from 4teamwork/lg-set-default-values-after-adding-to-container

DxBuilder: Only determine default values *after* object has been added to container.
Revert "DxBuilder: Fixed discriminators for default value adapter lookup."

This reverts commit bf45f133656fb925e47d8a45295cae6522dbf39f.
The reverted commit was based on a wrong assumption: The adapted context
for default value adapters is actually *supposed* to be the container
for add forms, therefore the previous behavior of ftw.builder was correct.

Conflicts:

	docs/HISTORY.txt
Revert "DxBuilder: Only determine default values *after* object has been added to container."

This reverts commit 6383d83733965d36986d3ec48e1291488682598d.
(Not needed anymore after reverting previous commit).

Conflicts:

	docs/HISTORY.txt
DxBuilder: Fix encoding problem when filling default value for "owners" field.