Update RTD documentation. (docstrings, changelog, documentation refactors)

Description

1. Update Installation instructions. (Based on README.md)
2. Remove AGIPD64k from available detectors to calibrate.
3. Add changelog.rst
4. Expose cal_tools and xfel_calibrate functions' docstrings
5. Refactor the documentations.

How Has This Been Tested?

Relevant Documents (optional)

Types of changes

• Docs (changes to the documentation)
• Refactor (refactoring code with no functionality changes)

Checklist:

• I have updated the documentation accordingly.

Reviewers

@calibration

docs/source/conf.py

@@ -62,12 +62,6 @@ sys.path.append(os.path.abspath("../pycalibration/"))
 p = Popen(["./makeAllDocs.sh"])
 p.communicate()
 
-import mock
-autodoc_mock_imports = ['Cython']
-
-MOCK_MODULES = ['numpy', 'matplotlib', 'matplotlib.pyplot','Cython']
-for mod_name in MOCK_MODULES:
-    sys.modules[mod_name] = mock.Mock()
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']