No function for accessing cluster basis in lattice cluster

Fixes #298

had to update Schott glass catalog download URL since this was causing our documentation build to fail.

src/GlassCat/data/sources.txt

@@ -1,7 +1,7 @@
 NIKON a49714470fa875ad4fd8d11cbc0edbf1adfe877f42926d7612c1649dd9441e75 https://www.nikon.com/products/components/assets/pdf/nikon_zemax_data.zip
 OHARA 0c9021bf11b8d4e660012191818685ad3110d4f9490699cabdc89aae1fd26d2e https://www.oharacorp.com/xls/OHARA_201130_CATALOG.zip
 HOYA b02c203e5a5b7a8918cc786badf0a9db1fe2572372c1c163dc306b0a8a908854 http://www.hoya-opticalworld.com/common/agf/HOYA20210105.agf
-SCHOTT 02c3212e6984a553994caf7533c6c08f284f6ebc9312dbf90e605226577577e8 https://www.schott.com/d/advanced_optics/6959f9a4-0e4f-4ef2-a302-2347468a82f5/1.32/schott-optical-glass-overview-zemax-format.zip
+SCHOTT 02c3212e6984a553994caf7533c6c08f284f6ebc9312dbf90e605226577577e8 https://mss-p-009-delivery.stylelabs.cloud/api/public/content/a79c07aa61da4c05a2c0bbab93d09a7f?v=3b65e351&download=true
 SUMITA fad12bfb1754ee9e33f7a6ec65c784c1dd1b8e87fde1ac2e440d24e85630c758 https://www.sumita-opt.co.jp/en/wp/wp-content/themes/sumita-opt-en/download-files.php files%5B%5D=new_sumita.agf&category=data
 ARCHER 7df8c42fb499720165c86d77dc8065db5126541a71b4e9d6a4849e27b25dd82d https://raw.githubusercontent.com/nzhagen/zemaxglass/master/AGF_files/archer.agf
 ARTON d214e050f7330257c8cfcd517b1f35b64077dac62cf2729f73b3723e00a59263 https://raw.githubusercontent.com/nzhagen/zemaxglass/master/AGF_files/arton.agf