1.5.9 - Buncha Bugfixes

We had been planning to wait on completion of a few new features for the next release, but too many changes have accumulated and people need to get the new version with all the fixes in, so this is being released now.

As you can see (reordered from changelog) we have a lot of fixes and maintenance.

* Bugfix - Correct Flash.h issues.
* Bugfix - Remove boot_opt.h which is not applicable to modern AVRs.
* Bugfix - Remove the useless dummy app that forced us to use avr-size -A to see the size of the bootloader separated from the app, and switch avr-size -A to normal avr-size to take advantage of this.
* Bugfix - Correct critical defect in disabled millis.
* Bugfix - Optiboot did not honor entry conditions (#452), bump optiboot version to 0x1A02.
* Bugfixes, several, for SerialUPDI, and improvements in error messages.
* Bugfix - Correct compilation when analogWrite() was used on AVR EA.
* Bugfix - Add missing API extensions on EA-series for ADC.
* Bugfix - Fix Comparator, Event, and SPI and Wire up well enough that things at least compile on EA. And in the case of comparator, SPI, and Wire, I'm pretty sure they work too.
* Bugfix - Optiboot boards did not honor the FLMAP option.
* Bugfix - in several cases it was possible to, using third party IDEs, pass incompatible options to the core. This now produces a more helpful error message. (#477)
* Maintenance - Correct CI testing to specify valid option for flmap menu.
* Maintenance - add CI testing for EA-series parts.
* Maintenance - Rebuilt all bootloaders in support of above fix. [flash.h fixes]
* Maintenance - Rebuilt all bootloaders again. [for entry condition fixes]

And very few new features:

* Docs: Major updates across the board, some long files have a ToC now. 
* Enhancement - implement `_getCurrentMillisTimer()`  and `_getCurrentMillisState()` which are/will be required for sleepTime.h
* Enhancement - Add the 16k and 32k EA-series parts. Still no 8k ones or headers for them either.
* Enhancement - (also makes the CI easier) Lay ground work for future library support for a Flash.h for Ex-series.
* Enhancement - Update forward looking EB-series defines now that headers have escaped (here's the bad news: 4 independent channels only, half of the WO channels are inverted waveforms with dead time insertion for PSC and BLDC drive applications - and TCF at most gets you 2 8-bit channels through a TCB-like method - it's meant for generating square waves or periodic pulses. The quality of the 4 good PWM channels we get may be unmatched (we'll need to see the docs - but it looks like 19-bit PWM resolution may be in the cards with HIRES. That will have to wait until we have datasheets though.
* Enhancement Add CORE_HAS_ERRORFUNS #define. Add CORE_HAS_MILLISSTATE