Refactor code. Various fixes.

* extract_tag(): Fix for tags content at end of description. Insert tag variable
  directly after delimiter. Fix for tag content that starts with blank line.

* insert_tag(): Remove function.

* insert_tags(): New function to insert tag_* variables at start of script.

* insert_script_tags(): New function for script_tag() calls within description.

* rm_multi_rev_test(): Remove function.

* insert_rev_include(): New line adjust. Close content.

* already_extracted(): Rename to tag_already_extracted().

* main(): Update todo. Use new functions adequately.