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

src/xfel_calibrate/notebooks.py

@@ -52,15 +52,6 @@ notebooks = {
                             "cluster cores": 1},
                },
     },
-    "AGIPD64K": {
-        "DARK": {
-            "notebook":
-                "notebooks/AGIPD/playground/AGIPD_SingleM_test_Dark.ipynb",
-            "concurrency": {"parameter": None,
-                            "default concurrency": None,
-                            "cluster cores": 4},
-        },
-    },
     "LPD": {
         "DARK": {
             "notebook": "notebooks/LPD/LPDChar_Darks_NBC.ipynb",