Some changes to the folder structure

Some changes to the folder structure

Compatibiltity issue with SAMD solved

• Enum definition "PORT" caused issues. Renamed to MCP_PORT.
• Took out the architecture deifitions out of library.properties, because misleading.

ESP8266 compatibility in library.properties confirmed

Small change in library.properties

Variable type conversion issues amended

The Arduino IDE Compiler gave some warning with regards to variable conversions for some functions (int to STATE). This has been solved.

Initial Release

First Version of the MCP23017 library