cxx: Added examples and tutorial for C++ binding

cxx: Added examples and tutorial for C++ binding

Summary:
Added the following examples:
* bg_cxx_example_01
* bg_cxx_example_02
* bubble_cxx_example_01
* button_cxx_example_00
* button_cxx_example_01
* calendar_cxx_example_01
* calendar_cxx_example_02
* calendar_cxx_example_03
* calendar_cxx_example_04
* calendar_cxx_example_05
* clock_cxx_example
* datetime_cxx_example
* glview_cxx_example_01
* hoversel_cxx_example_01
* icon_cxx_example_01
* location_cxx_example_01
* menu_cxx_example_01
* popup_cxx_example_01
* radio_cxx_example_01
* separator_cxx_example_01
* slider_cxx_example
* spinner_cxx_example
* table_cxx_example_01
* table_cxx_example_02
* thumb_cxx_example_01

Added documentation for the above examples, as well as how using lambdas
with C++ elm binding. How to use autohide feature and how to use the C++
wrappers to create windows, widgets and call Eo functions from them with
automatic C++ type conversion and how to use signals from C++.