I2C port configurable

[hreuver]

Currently I'm using Openplotter on an Odroid.
Difference between Odroid and  Pi4 is mainly /dev/i2c-2 vs /dev/i2c-1 and the lack of integrated wifi.

I don't use Openplotter-Wifi since I can use the tools from the distribution for that.
The difference in I2C ports cause a lot of small nagging problems, which should not be there if the software was generic.
Hardcoding the I2C ports speeds up the development in short term, but I believe it will ultimately causes more problems then necessary.

With regards,
HR

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Of the Raspberry-only tools I guess the ones below should work with minimal changes:
- Xygrib
- I2C sensors
- Pypilot

I haven't tried the Moitessier HAT, 1W and analog sensors.
I2C works mostly if I make a softlink from /dev/i2c-2 to /dev/i2c-1, but the mpu9250 fails currently.

Canboat can be installed using "apt-get --build source ...".
With canboat, openplotter-can and signalK also work.
I expect Xygrib to work to work in the same way.

My current system is Ubuntu 18.04 with the extra packages from OpenPlotter as below:

openplotter-can                           2.1.0-stable
openplotter-dashboards              2.1.0-stable
openplotter-i2c                            2.1.0-stable
openplotter-pypilot                      2.0.7-beta
openplotter-settings                    2.2.0-stable
openplotter-signalk-installer        2.1.0-stable
canboat                                       1.2.4-stable
xygrib                                          1.2.7 (github)

The OpenCPN installer works generally, but I currently use OpenCPN from github with more and newer plugins than OpenPlotter can provide right now.
(Until the package manager from OpenCPN becomes fully operational I guess.)