Gerbview: Add support for recent File Format Attribute metadata, both for X2 Gerber file format and X1 (R274X) format.
Pcbnew already uses this attribute when creating Gerber files.
Because Gerber files using this attribute identify the board layers stackup, Gerbview (if this attribute is defined) can sort gerber images stach up like the board.
(in layer manager, just right click to access to the sort menu)
Eeschema: Netlist generator: remove option to generate the fully outdated old netlist file format (based on a very old Orcad netlist format)
Only the new (S expression) better netlist file format is now used.
Grebview: add info in layer manager for Excellon drill filles, similar to X2 file function info in X2 gerber files.
pcbnew: Unconnected items share the same NETINFO_ITEM, even if on different boards.
pns: Non-copper pads are not treated as obstacles.
Missing fixes for the revision 5301.
Fixed typo.
OSX build fixes.

* Make defintion of OSX build target a requirement.
* Update OSX build documenation to reflect build changes.
* Update OSX build script to reflect build changes.
Factor out some common code in hotkeys_module_editor.cpp
Modify GetCenter and Rotate functions in DRAWSEGMENT to act according to the type of the edge
Add duplicate and exact move tools to modedit

These are accessible via the context menu, and via hotkeys
WIP: Get move exact working in the GAL modes too
Duplicate now works with selections
Only handle move exact once, even though it seems odd to not handle it here...
Increment pad numbers when duplicating. Move pad number incrementing into the D_PAD and MODULE classes
Fix display of selection info after duplicating in GAL
Fix comment regarding move exact
Fix undo of move exact - use UR_CHANGED
Remove dulplicate function stub and transition from EDIT_TOOL - how duplicate would work in pcbnew is unclear