Py-rate

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Added
+++++
- Python 3.7 support.
- Optional ``conv2tif`` step.
- Building of docs integrated with Travis CI.
- Coherence masking, view coherence masking section in ``input_parameters.conf``
for options.
- Input parameter validation.
- SLC and coherence file lists for file discovery.
- Create quick view png for rate map product.
- Add support for reading interferogram in Geotiff format.
- Add detailed validation and hints for configuration parameters
- Add system tests for all 3 types of input formats

Changed
+++++++
- ``linrate`` step has been renamed to ``process``.
- ``postprocess`` step has been renamed to ``merge``.
- ``converttogeotiff`` step has been renamed to ``conv2tif``.
- CLI structure: config files now need to be provided with ``-f`` flag.
- Reduced console output, default verbosity setting is now ``INFO``.
- Restructure of code layout, src modules now in ``PyRate/pyrate/core`` directory
and scripts at ``PyRate/scripts``.
- Reference pixel values are expected to be in latitude and longitude values.

Removed
+++++++
- Unused luigi code.
- References to Matlab.
- Unused tests for legacy api.

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Added
+++++
- ``utils/apt_install.sh`` script that lists Ubuntu/apt package requirements.
- ``utils/load_modules.sh`` script that sets up NCI Raijin HPC environment.

Fixed
+++++
- Errors being caused by newer version of ``networkx``; v2.3 now supported.

Removed
+++++++
- Unused Python and OS packages.
- environment.yml - conda env will now be installed using ``requirements.txt``.
- HPC directory - hpc README.rst moved to docs.
- setup.cfg - no longer needed.
- Luigi functionality - hasn't been operational and is reported as vulnerable.
Single machine parallelism is achieved with joblib.

Changed
+++++++
- Requirements now managed by ``requirements.txt`` file, parsed by ``setup.py``.
- Requirements now split across base ``requirements.txt`` and separate files
for dev (``requirements-dev.txt``) and testing (``requirements-test.txt``).
- Moved default config files to top level source directory.
- Pinned Python dependencies to specific versions.
- Travis build now installs GDAL from apt.
- Travis only builds on master, develop and \*-travis branches.
- Consolidated documentation into ``PyRate/docs``.
- Updated install instructions for Ubuntu and NCI.

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- Stable beta release.

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- First release on PyPI.