Added new fields: usernamefield and fix in passwordfield

paramecio/cromosoma/extrafields/usernamefield.py

@@ -0,0 +1,16 @@
+from paramecio.cromosoma.corefields import PhangoField
+from paramecio.cromosoma.coreforms import PasswordForm
+from hmac import compare_digest as compare_hash
+import crypt
+import re
+
+class UserNameField(PhangoField):
+        
+    def check(self, value):
+        
+        if not re.match("^[A-Za-z0-9_-]+$", value):
+            self.txt_error='Error: use only letters, numbers, underscores and dashes for this field'
+            self.error=1
+            value=''
+            
+        return value