ATMEGA8U2 symbol added to atmel.lib
ATEMEGA8U2 in atmel.lib updated to match library conventions

* Pin ends aligned to 100mil grid
* Vcc and GND pins moved to top and bottom respectively
Description added for ATMEGA8U2 in atmel.dcm
ATMEGA8U2 symbol improved

* XTAL1 set to input pin type
* UVCC, D+, D-, UGND pins rearranged
* RESET, SS, HWB, CTS, RTS overscored in pin description
* QFN-32-1EP added to footprint list
Aliases ATMEGA16U2 and ATMEGA32U2 added to ATMEGA8U2
Merge pull request #47 from arunisaac/atmega8u2

ATmega8U2/16U2/32U2 symbol added to atmel.lib