Fast: I2C burst mode writes

Thanks to @birdwes contribution to make the I2C (wire) writes a lot faster and detect and fix a bug.

• Faster Writes (I2C burst mode)
• Bug fix about changes in frequencies, a rare bug detected by @birdwes

Feedback is appreciated.

Version 0.5: firmware space optimization, we save as much as 1K of firmware now.

By using only integer math we saved a little more than 1k of your precious firmware space now, plus other minor bugs and some validations.

Thanks to CO7RR Josue to take the time with me to understand the math behind it.

Implemented a boolean array to check the status of the clocks si.clkOn[clk] if true then that clk is active.

As usual docs are update to reflect changes and correct typos.

Improved initialization, I2C handling and bug fix.

A new version, with all this goodies:

• Improved init procedures (now mandatory)
• Internal I2C handling (no need to explicit declare and init before hand)
• Fixed a bug on the correction procedure.

See ChangeLog.md file for more details.

First full featured release candidate

This release candidate has all the wanted features by now.

If after some time it does not develop any new bug it will be declared stable.