Update documentation for deprecated method of DataProvidersManager

src/site/markdown/configuration.md

@@ -27,7 +27,7 @@ into `orekit-data` and add the following lines at the start of your program (bef
 first time):
 
     File orekitData = new File("/path/to/the/folder/orekit-data");
-    DataProvidersManager.getInstance().addProvider(new DirectoryCrawler(orekitData));
+    DataContext.getDefault().getDataProvidersManager().addProvider(new DirectoryCrawler(orekitData));
 
 This is sufficient to start working.
 

src/site/markdown/downloads.md

@@ -76,7 +76,7 @@ file from the forge, to unzip it anywhere you want, rename the `orekit-data-mast
 into `orekit-data` and add the following lines at the start of your program:
 
     File orekitData = new File("/path/to/the/folder/orekit-data");
-    DataProvidersManager manager = DataProvidersManager.getInstance();
+    DataProvidersManager manager = DataContext.getDefault().getDataProvidersManager();
     manager.addProvider(new DirectoryCrawler(orekitData));
 
 This file contains the following data sets. Note that the data is updated only

src/site/markdown/faq.md

@@ -85,7 +85,7 @@ file from the forge, to unzip it anywhere you want, rename the `orekit-data-mast
 into `orekit-data` and add the following lines at the start of your program:
 
     File orekitData = new File("/path/to/the/folder/orekit-data");
-    DataProvidersManager manager = DataProvidersManager.getInstance();
+    DataProvidersManager manager = DataContext.getDefault().getDataProvidersManager();
     manager.addProvider(new DirectoryCrawler(orekitData));
 
 Using a folder allows one to change the data in it after the initial download, e.g., adding new EOP files as they