Add Static Library project

[fburel]

In this pull request, I have separated the core class in a static lib (EspTouchLib.a)
The EspTouchDemo project only reference this library.
To use the library in another project :

create an 'include' folder in your project root directory
copy the ./Library/EspTouch folder in your include directory
in your project Build Phases, section link Binary With Libraries, add a reference to libEspTouch.a
in your project build Setting, add a new header_search_path with the value : "$SOURCE_ROOT/include"
add #import "EspTouch/ESPTouch.h" in your code source when you need to access EspTouch classes
I think providing the code as this will improve the understanding and will make it easier to maintain rather than having 2 separate repo (1 for the lib and one for the actual code)

[muhammadfaheem-pycom]

I think now its time to shape this repo as SDK for ios