* Summary of changes:
* Initial support for drawing lines. (Thanks to Algorith for applying my perspective_matrix patch.)
* The distance value (in BUs) is also drawn in the 3D view now.
* Also fixed some wrong calculations of global/local distances.
* Now it's really "what you see is what is calculated".
* Use bl_addon_info for Add-On information. Use "3D View" in category & name
* Renamed reenter_editmode to view3d.reenter_editmode.
* Renamed panel_measure.py into space_view3d_panel_measure.py
* Active object is only used for edit-mode now. Measurement with exactly one sel. (but not necessarily active) object now gets the obj via the sel-object array.
* API change Mathutils -> mathutils (r557)
* Reduced PRECISION to 4
* Deselecting 1 of 2 objects now works correctly (active object is ignored).
* Force a redraw of the area so disabling the "measure_panel_draw" checkbox will clear the line/text.
* Only calculate area (CPU heavy) if a "area" checkbox is enabled.