Lot of corrections.

Corrected issue of analogReference() dbuezas#27
SRAM capacity added to boards.txt dbuezas#206
The accidentally swapped PE5 & PE6 corrected dbuezas#185
More analog inputs available dbuezas#130 and dbuezas#123 (reply in thread)
Wrong analogReadResolution() on boot has been corrected dbuezas#130 and dbuezas#41
External oscillator and divided clocks has been added dbuezas#119
More and LGT8F specific interrups available dbuezas#40
Corrected LGT8F328D reference voltage (VCAL1) calibration value issue dbuezas#156
Better delayMicroseconds(), Arduino EEPROM API, and even more things dbuezas#191