eeschema: Operations on blocks inner selection

[Eldar Khayrullin]

It will be usefull add selection tool that selects only elements in block with mouse.
Now mouse selection catch all elements that touch to block rect.

Application: kicad
Version: 201609160817+7160~55~ubuntu16.04.1-, release build
Libraries: wxWidgets 3.0.2
           libcurl/7.47.0 OpenSSL/1.0.2g zlib/1.2.8 libidn/1.32 librtmp/2.3
Platform: Linux 4.4.0-36-generic x86_64, 64 bit, Little endian, wxGTK
- Build Info -
wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8)
Boost: 1.58.0
Curl: 7.47.0
KiCad - Compiler: GCC 5.4.0 with C++ ABI 1009
        Settings: USE_WX_GRAPHICS_CONTEXT=OFF
                  USE_WX_OVERLAY=OFF
                  KICAD_SCRIPTING=ON
                  KICAD_SCRIPTING_MODULES=ON
                  KICAD_SCRIPTING_WXPYTHON=ON
                  BUILD_GITHUB_PLUGIN=ON
                  KICAD_USE_SCH_IO_MANAGER=OFF
                  KICAD_USE_OCE=ON

[Jon Evans (craftyjon)]

This will come as part of GAL port for Eeschema