Adding UNDO flag to import operators. Made this only for trunk addons.

patch [#27769] Small fixes for X3D exporter: not existing IndexedTriangleSet.creaseAngle, zero Viewpoint.orientation, ...

*Info from the tracker submission this patch resolves*

3. When exporting texture URL, new Blender 2.58 exporter writes URLs in the order: [basename, result of bpy_extras.io_utils.path_reference, absolute]. I propose to change this order to write the result of bpy_extras.io_utils.path_reference *first*. Reasons:
-- Result of bpy_extras.io_utils.path_reference is controlled by user (through path_mode). By setting it correctly, user can make sure that 1st url matches (which is nice for 3d viewer, also avoids warnings from view3dcene that one url along the way was not available).
-- This also makes the results of 2.58 exporter more similar to how 2.57 behaved. In 2.57, the relative path "os.path.relpath(filepath_full, relpath)" was first, then basename, then absolute name. And that was good, in my opinion, as relative path has the best chance of success and is more directly controlled by user. (New "bpy_extras.io_utils.path_reference" is even better, so kudos for implementing it.)

4. Finally, a trivial fix to the formatting of output "<TextureTransform..." in X3D. Without this fix, "<TextureTransform" and "translation=" are on the same output line, separated by a lot of whitespaces (taken from ident_step).

bug #2, zero length axis.

previous order deprecated.

- remove/comment unused variables
- remove unused imports
- fixed some bugs using incorrect variables

fix issue #1 from bug [#27896] B258.0 > X3D export > 3 bugs: "MA_Black".001, lib groups, Rotation 0 0 0 0

- h3d: replace unfinvviewmat with gl_ModelViewMatrixInverse

object hierarchy (parent/child) support for X3D export, tested with dupli-groups, scaling, rotations.
keep this optional so exporting without hierarchy is still supported.