Bug fixes for 1.5.2

NOTE:
- Fixed an issue related to edges highlight in Tweak and Sculpt that was crashing wings when the object have hidden faces or holes. Thanks to Extrudeface for report it. [Micheus]
- Fixed a issue related to Select Group and Saved Camera windows not be drawn using the alpha settings as defined in the preferences. Thanks to Justanother1 for report it. [Micheus]
- Fixed the duplicated IDs in the language file for "Rename" operations available in the "Geometry Graph" window. Thanks to TulipVorlax. [Micheus]
- Fixed some inconsistencies in the file generated by the Collada plugin exporter. [Micheus]
- Fixed some issues related to images of materials exported by POV-Ray plugin. Thanks to RyMopar that reported it. [Micheus]
- It was also fixed an error in the "wings_u:relative_path_name" routine that was rebuilding the full path in a wrong way. [Micheus]