=== Custom Transform Orientation ===

Custom Orientations can be added with Ctrl-Shift-C (hotkey suggestions are welcomed), this adds and select the new alignment. Custom Orientations can also be added, deleted, selected from the Transform Orientations panel (View -> Transform Orientations). Standard orientations (global, local, normal, view) can also be selected from this panel.

If you plan on using only a single custom orientation and don't really need a list, I suggest you use the hotkey as it adds and selects at the same time.

Custom Orientations are save in the scene and are selected per 3D view (like normal orientation).

Adding from an object, the orientation is a normalized version of the object's orientation.
Adding from mesh data, a single element (vertex, edge, face) must be selected in its respective selection mode. Vertex orientation Z-axis is based on the normal, edge Z-axis on the edge itself (X-axis is on the XoY plane when possible, Y-axis is perpendicular to the rest). Face orientation Z-axis is the face normal, X-axis is perpendicular to the first edge, Y-axis is perpendicular to the rest.
(More logical orientations can be suggested).

I plan to add: 2 vertice (connected or not) => edge orientation , 3 vertice = face orientation

Differences from the patch:
- orientations no longer link back to the object they came from, everything is copy on creation.
- orientations are overwritten based on name (if you add an orientation with the same name as one that already exists, it overwrites the old one)