Tidy loop in org-dotemacs-load-blocks

Use single setq statement instead of two.

Altered items:
org-dotemacs-load-blocks
Print error messages after finishing org-dotemacs-load-blocks

Altered items:
org-dotemacs-load-blocks
Bugfix: org-dotemacs-extract-subtrees

Put loop form back inside unless condition where it should be.

Altered items:
org-dotemacs-extract-subtrees