Library configuration file management (issue #1734)

When an application uses a library supporting configuration:
- the library configuration file is stored in the sketch folder as a
project ressource.
- a sketch tab is created in Arduino IDE to edit the library
configuration file

This commit manages following actions:
- create configuration file tab when opening a sketch which uses a
Library configuration file
- copy the configuration file in the sketch folder and create a
configuration file tab when importing a library which uses a library
configuration file
- add the library configuration file (from sketch) as include file when
compiling the library only

Added as an example, Morse library supporting configuration file