Make setup_orekit_curdir optionally load data from folder

This is a proposal to allow loading Orekit data from a folder. In my case, it speeds up the startup of my Python application a lot.

The two commits are actually 2 options:

1. The existing setup_orekit_curdir function was modified with an extra optional argument.
2. The os module is used to detect if the filename argument is a file or a folder.

python_files/pyhelpers.py

@@ -24,9 +24,10 @@ import shutil
 from datetime import datetime
 
 import math
+import os
 from java.io import File
 from orekit import JArray
-from org.orekit.data import DataProvidersManager, ZipJarCrawler
+from org.orekit.data import DataProvidersManager, ZipJarCrawler, DirectoryCrawler
 from org.orekit.time import TimeScalesFactory, AbsoluteDate
 from org.orekit.utils import ElevationMask
 
@@ -58,22 +59,27 @@ def download_orekit_data_curdir(filename='orekit-data.zip'):
 def setup_orekit_curdir(filename='orekit-data.zip'):
     """Setup the java engine with orekit.
 
-    This function loads the orekit-data.zip from the current directory
-    and sets up the Orekit DataProviders to access it.
+    This function loads the Orekit data from either:
+        - A zip in the current directory (by default orekit-data.zip),
+        - A folder,
+    depending on whether `filename` is the path to a file or to a folder.
+
+    Then the function sets up the Orekit DataProviders to access it.
 
     The JVM needs to be initiated prior to calling this function:
 
         orekit.initVM()
 
     Args:
-        filename (str): Name of zip with orekit data. Default filename is 'orekit-data.zip'
+        filename (str): Name of zip or folder with orekit data. Default filename is 'orekit-data.zip'
+
 
     """
 
     DM = DataProvidersManager.getInstance()
     datafile = File(filename)
     if not datafile.exists():
-        print('File :', datafile.absolutePath, ' not found')
+        print('File or folder:', datafile.absolutePath, ' not found')
         print("""
         
         The Orekit library relies on some external data for physical models. 
@@ -90,7 +96,12 @@ def setup_orekit_curdir(filename='orekit-data.zip'):
         
         """)
 
-    crawler = ZipJarCrawler(datafile)
+    if os.path.isdir(filename):
+        crawler = DirectoryCrawler(datafile)
+    elif os.path.isfile(filename):
+        crawler = ZipJarCrawler(datafile)
+    else:
+        print('filename ', filename, ' is neither a file nor a folder')
     DM.clearProviders()
     DM.addProvider(crawler)