MAINT: make more dependencies optional

setup.py

@@ -155,12 +155,16 @@ def setup_package():
         author='Henrik tom Wörden',
         author_email='h.tomwoerden@indiscale.com',
         install_requires=["caosdb>=0.6.0",
-                          "openpyxl>=3.0.0",
                           "pandas>=1.2.0",
                           "numpy>=1.17.3",
-                          "xlrd>=2.0",
                           ],
         extras_require={"h5-crawler": ["h5py>=3.3.0", ],
+                        "table-importer": [
+                            "xlrd>=2.0",  # indirectly via pandas
+                        ],
+                        "scifolder": [
+                            "openpyxl>=3.0.0",  # indirectly via pandas
+                        ],
                         },
         packages=find_packages('src'),
         package_dir={'': 'src'},