Fix T63663: Object mode proportional editing affects objects which are disabled for selection

Objects which are not selectable are no longer affected by
proportional transformations.

Fix T63247: edbm_rip_invoke__edge rips unselected verts on mesh borders

Ripping edges would in some cases rip verts on unselected edges. This is now fixed so that we only rip verts from the actually selected edges.

Reviewed By: Brecht

Differential Revision: http://developer.blender.org/D4646

Fix T63429: Random deselect function lost

Add back the ability to choose the select operation for random select.
Now we allow the operator to specify if the select operation should be
visible in the GUI or not.

Reviewed By: Brecht

Differential Revision: http://developer.blender.org/D4665

Fix T63341: Xray mode makes some shading popover options grayed out despite them working

Do not gray out shading items if the xray alpha value is 1.
They are rendered correctly in viewport so there is no reason to mark
them as disabled in the shading menu.

Fix T63467: Edge/vertex selection isnt working properly with X-ray set to 1

Edit mode shows the mesh elements in X-ray mode even if alpha is set to
1. Now the code takes this into account so that you can still select
visible mesh elements in X-ray edit mode.

view3d_draw_legacy need to be updated with the new XRAY flag macros to
avoid crashes. Additional cleanup of the XRAY macro flags were done.

Fix T62114: Wireframe mode selection: selects backside objects when clicking frontside object in 3d-window

Now the depth order of objects when trying to select them is only used when not in X-ray mode.
Before, this was only the case in wireframe mode regardless of X-ray settings.

I've also unified the usage of V3D_XRAY and XRAY_FLAG as they were basically copies of each other.

Reviewed By: Clément

Differential Revision: http://developer.blender.org/D4504

Fix T63281: Drivers inside nodegroups inside nodegroups don't show up in Driver Editor

Recurse into node groups when looking for drivers.

Reviewed By: Brecht

Differential Revision: http://developer.blender.org/D4653

Fix T63120 Select random in particle edit mode is broken

Fix coding snafu where the variable keeping track of changes only took
the state of the last element into account.

Fix T63086: Navigation problem with Background/Reference Images

The issue was the manipulated depth for images would be used when doing distance depth checks.
Now we will use the actual depth of the image object when doing such tests.

Reviewed By: Clément Foucault

Differential Revision: http://developer.blender.org/D4616

Fix T60421: Bone heads are hidden when non-connected parent is hidden

The root point of a bone is now always drawn unless it is connected to an other bone.

Reviewed By: Clément Foucault

Differential Revision: http://developer.blender.org/D4194