Ported to new i2cdevice API, bugfixes

[Gadgetoid]

Details here - pimoroni/i2cdevice-python#3

Have also tidied up ths bindings- combining some individual registers into i2cdevice virtual registers for automatic bit twiddling- so this will need some thorough testing.

• Corrected a bug in am/pm and 12 hour time format- 12 hour time was 1-bit short and the am/pm flag was one bit to the right.
• Combined UNIX_TIME into one 32bit register, i2cdevice automatically handles this
• Combined USER_RAM into one 16bit register, again i2cdevice handles shifting & twiddling
• Combined PASSWORD into one 32bit register
• Combined TIMER_VALUE and TIMER_STATUS into 16bit (actually 12bit) registers
• Combined version and id into one CHIP register, i2cdevice handles masks and shifts

TODO: Check I haven't horribly broken the byte order of the above combined >8bit regs.