Ethernet library to version 1.1

Version 1.1 of the Ethernet library brings the following improvements:
* support for W5500 and W5200 Wiznet chipsets
* automatic detection of the Wiznet chipset
* SPI speed set to 14MHz, maximum allowed by the W5100 chipset
* generalized SPI_CS pin handling functions
* added getMaxSockets() method
* improved 3rd party compatibility using the SPI Extended API as a criterion of choice 
* removed redundant configurations and useless variable modifiers