pcbnew: confirnation missed deleting locked components

[Sergey A. Borshch]

Pressing "Delete" key while mouse pointer is inside of locked component silently delete component, while selecting "Delete footpinnt" item from dropdown menu displays message that footprint is locked.

Application: pcbnew
Version: (2016-01-25 BZR 6513)-product release build
wxWidgets: Version 3.0.0 (debug,wchar_t,compiler with C++ ABI 1002,GCC 4.8.4,wx containers,compatible with 2.8)
Platform: Linux 3.19.0-39-generic x86_64, 64 bit, Little endian, wxGTK
Boost version: 1.54.0
         USE_WX_GRAPHICS_CONTEXT=OFF
         USE_WX_OVERLAY=OFF
         KICAD_SCRIPTING=OFF
         KICAD_SCRIPTING_MODULES=OFF
         KICAD_SCRIPTING_WXPYTHON=OFF
         USE_FP_LIB_TABLE=HARD_CODED_ON
         BUILD_GITHUB_PLUGIN=OFF

[Wayne Stambaugh (stambaughw)]

I committed a partial fix for this the product branch r6601. The delete hot key will no longer delete locked footprints but it will also not give you any warning that the footprint is locked and allow you to override the lock. I'm personally not a big fan of nagware so I'm reluctant to add a message dialog. I would prefer just displaying a warning in the message panel but that may not be preferred by all users. The code that handles this is a bit ugly so I have to do some code cleaning before I add some type of indicator that the user is attempting to delete a locked footprint.