Add missing elements in standalone parser

Add:
- missing imports
- __version__ variable

Additionally regenerated json parser example

lark/exceptions.py

@@ -1,8 +1,9 @@
-import logging
-
 from .utils import STRING_TYPE
 
 ###{standalone
+import logging
+
+
 class LarkError(Exception):
     pass
 

lark/tools/standalone.py

@@ -88,6 +88,8 @@ def main(fobj, start):
     lark_inst = Lark(fobj, parser="lalr", lexer="contextual", start=start)
 
     print('# The file was automatically generated by Lark v%s' % lark.__version__)
+    print('__version__ = "%s"' % lark.__version__)
+    print()
 
     for pyfile in EXTRACT_STANDALONE_FILES:
         with open(os.path.join(_larkdir, pyfile)) as f:

lark/tree.py

@@ -4,10 +4,12 @@ except ImportError:
     pass
 
 from copy import deepcopy
-from collections import OrderedDict
 
 
 ###{standalone
+from collections import OrderedDict
+
+
 class Meta:
     def __init__(self):
         self.empty = True