Recursive directories dataset capability (#1408)

* Recursive directories dataset capability

* x.split('.')[-1]

* f += glob.glob(f"{p}{os.sep}**.*", recursive=True)

* f += glob.glob(str(p / '**.*'), recursive=True)

* remove . from image and vid formats

* .txt to txt

* str(p / '**' / '*.*')

utils/general.py

@@ -79,9 +79,9 @@ def check_dataset(dict):
     # Download dataset if not found locally
     val, s = dict.get('val'), dict.get('download')
     if val and len(val):
-        val = [os.path.abspath(x) for x in (val if isinstance(val, list) else [val])]  # val path
-        if not all(os.path.exists(x) for x in val):
-            print('\nWARNING: Dataset not found, nonexistent paths: %s' % [*val])
+        val = [Path(x).resolve() for x in (val if isinstance(val, list) else [val])]  # val path
+        if not all(x.exists() for x in val):
+            print('\nWARNING: Dataset not found, nonexistent paths: %s' % [str(x) for x in val if not x.exists()])
             if s and len(s):  # download script
                 print('Downloading %s ...' % s)
                 if s.startswith('http') and s.endswith('.zip'):  # URL