- implementing COMPS_Doc* objects validation postponned
- display_order is now optional parameter (doesn't appear in xml output if not set)
- group, environment and category has empty output if don't contains any
-   group_id/option_id/package
- python sequence and comps_objlist _remove method was added, removing
-   concrete object from list
- build_prep fixed
- missing display_order fix for libcomps.Environment
- PyCOMPS_Sequence.__getitem__["objectid"] implemented for libcomps.GroupList, libcomps.CategoryList, libcomps.EnvList