[ek_tm4c123gxl] use different pin for PCD8455 CD so that I2C1 is free
[tests] enhance pong.js
[ssd1306] improve flip implmenetation
[graphics double buffering] add flip&mode canvas methods and js bindings
[graphics] ssd1306: default to double buffering
[graphics] remove canvas::mode_set() method
[graphics] adapt pong.js sample for  double buffering
[graphics] flip() canvas after operations
[graphics] pcd8544: double buffering default
[graphics] ssd1306: no need to flip() on fill()
[graphics] ssd1306,pcd8544: set address only once as part of init sequence
[graphics] ssd1306: bulk send of init sequence