Write unit tests + Move palmsplusr functions out of this repo

[vincentvanhees]

I copied some of the palmsplusr function in order to ease modifying them to work with HabitusGUI. Now these work, it is time to move them out again.

• Write unit-test for the individual palmsplusr functions that are now inside HabitusGUI.
• Merge revisions back into palmsplusr and/or create separate repository. At least it does not seem logical to have all code inside HabitusGUI

[vincentvanhees]

Regarding:

Merge revisions back into palmsplusr and/or create separate repository...

I have now decided to postpone this for a while:

• The new repository will not likely be used outside the context of HabitusGUI
• The new repository requires separate maintenance, I am a bit worried that we will be swamped with too many subprojects to look after
• Having everything in one place eases testing and bug fixing while HabitusGUI as a whole is still under development

Instead, i have now updated the HabitusGUI license to be more in line with the license as used by https://github.com/TheTS/palmsplusr

[vincentvanhees]

New plan: I will migrate all palmsplusr functionality inside HabitusGUI to a new package: https://github.com/habitus-eu/hbGIS

Motivation:

• The code may actually have value on its own in contrast to what I said above.
• The development is likely to broaden a lot and it may be easier to treat this as a separate package.
• Keeping the palmsplusr code inside HabitusGUI is not ideal as HabitusGUI should be about the GUI and not about all the data processing steps.

[vincentvanhees]

TO DO:

• Create branch with code replaced
• Update installation instructions
• Test with real data
• Make PR