updating codebase of lib

[orgua]

hi paul, i know you only anticipate PR for new hardware support because you say the lib has "very mature code", but this statement is simply not true. over the years it became a big patchwork of ancient or even useless code. there were several bugs to find. the most obvious one is in the bus-power feature. the function write_bit() always powers the bus without permission. I modernized and extended the interface of the lib without breaking old code. i did tests on several platforms. see list of changes below.
where do you see problems in merging this PR?

I would like to co-maintain the onewire-lib with you. Currently I have rebuild and maintained the https://github.com/orgua/OneWireHub project for emulating slave-devices and i would like to apply my experiences to the onewire-master-lib.

changes i made so far:

• real life tested with several platforms (atmega, atsamD21, Atsam3x, esp8266, esp32, teensy)
• extend and fix hardware support (specially esp-boards, esp32, ...)
• added travis CI for a big bunch of controllers
• delayMicroseconds() hardware abstraction to allow proper nRF51-use (redbear messed up the delaymicroseconds()-implementation)
  • will be removed as soon redbear fixes its code
• overload write() to replace write_bytes() and read() to replace read_byte()
• update code documentation, doxygen style
• allow to use internal pull-up if micro controller has support for it -> most µC support INPUT_PULLUP in combination with pinMode(), others will get an error message or warning if feature is enabled but not supported / tested
• clean up compiler-switches
• better implementation to allow parasitic power to bus, otherwise master will act as open-drain-only! -> this was totally wrong before as the bus was powered for a short amount of time even if powering is disabled
• extend examples with ds2438 and a bus-discovery feature
• clean up examples, easier to understand, more similar to each other
• put hardware dependant code into platform.h
• better naming of variables and a lot of code cleanup
• simplify pin-access and interrupt-handling
• improve onewire class-interface (it was possible to copy the object, ...)
• reduce size of data types if possible, more const correctness and much more explicit code
• get rid of most ancient c and cpp code and reduce language mix
• decide on one code style - Allman braces - was closest to main style in original
• a lot of how-to documentation for this lib inside this readme

[orgua]

Hi Paul,

it is hard to guess your thoughts when you say nothing at all.

• You will look into it in the next 1-6 month?
• You don't want any help maintaining the library, despite the comments in the code?
• You are categorically against documenting, modernizing and fixing the code?

[nomis]

This has the same problem as the original version (#79). You can't tell the difference between no devices and a shorted bus.

[orgua]

ok, it could be changed easily but brings one more comparison. and it will break old code. most codebases will only test for non-zero. On the other hand - a major version change should be allowed to break code (with proper documentation).
the most elegant solution (so old code still works) would be to add a register for error-codes that could be checked.