Ismn

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- Remove setuptools_scm from dependencies
- Remove option to pip install ismn[plot] for now.

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- Rewrite package, objects for Networks, Stations, Sensors etc.
- Update ISMN_Interface to use new components, similar behaviour to old interface.
- Add MetaVar and MetaData modules for ismn metadata handling.
- Data readers are now collected in filehandler class.
- Metadata for soil layers is now filter by the sensor depth.
- Support reading from zip archive and extracted folders.
- New python_metadata structure (no absolute paths, no pickle format).
- Drop support for old ceop format (new ceop_sep format is supported!).
- Move lookup tables to const.py
- Update docs and tests.
- Use Github Actions instead of Travis CI.

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- Update package pyscaffold package structure
- Drop python 2 support
- Add read function to ISMN_Interface
- Add travis pypi deployment
- Fix get_min_max_timestamp_header_values

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- Add function to initialise different network

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- Set allow_pickle to True when loading metadata

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- Update readme
- Added information about landcover and climate to metadata.