Merged lots of PR + fix some memory leaks

Fixed drawProgressBar

Updated URL in library.properties

Fixing a typo

cleanup compiler warnings

Standalone html page to graphically edit fonts

#143 Use virtual destructor on base class

Fix typo

Added getColor function

fix const condition check

Method to mirror the display

Fix warnings when compiling against GCC 5.4

correct type to avoid compiler warning

Allow for use of either 128x64 or 128x32 displays

Support for custom font table look-up function

Changed negative to positive sign at maxProgressWidth

Library did some allocs without free and lots of un-initialized variables.

Applied pull requests from esp8266-oled-ssd1306:

squix78/esp8266-oled-ssd1306#169
squix78/esp8266-oled-ssd1306#157
squix78/esp8266-oled-ssd1306#144

And applied the suggestions from issues:
squix78/esp8266-oled-ssd1306#170
squix78/esp8266-oled-ssd1306#161

Support multiple display resolutions

Applied PR from esp8266-oled-ssd1306:
squix78/esp8266-oled-ssd1306#133

Better Brightness / Contrast control

Suggestions taken from this issue:
squix78/esp8266-oled-ssd1306#134

It is now the same version as being used in ESPeasy.

Fixed Copy function

Replaced unicode arrows with html entities for broader compatibility