make description more succinct

Author: lixingwang

function/datetime/descriptor.json

@@ -34,7 +34,7 @@
         },
         {
             "name": "formatDate",
-            "description": "Format the date according to the specified format. The pattern of the formatter contains of MM(month), DD(day), YYYY(year) and delimiter, they are case insensitive, such as: MM-dd-YYYY or yyyy/mm/dd",
+            "description": "Format the date according to the specified format. The format uses MM(month), DD(day) and YYYY(year) and they are case insensitive",
             "example": "datetime.formatDate（\"02/08/2017\", \"dd-MM-yyyy\"）=> 08-02-2017",
             "args": [
                 {
@@ -52,7 +52,7 @@
         },
         {
             "name": "formatDatetime",
-            "description": "Format the datetime according to the specified format. The pattern of the formatter contains of MM(month), DD(day), YYYY(year), hh(hour), mm(minute), ss(second) and delimiter, they are case insensitive except MM, MM is case sensitive, upper case MM for month and lower case mm for minutes such as:MM-dd-YYYYdd-MM-yyyy T hh-mm-ss",
+            "description": "Format the date according to the specified format. The format uses MM(month), DD(day), YYYY(year), hh(hour), mm(minute) and ss(second), they are case insensitive except MM",
             "example": "datetime.formatDatetime（\"2017-04-10T22:17:32.000+0700\", \"dd/MM/yyyy T hh:mm:ss\") => 10/04/2017 T 22:17:32",
             "args": [
                 {
@@ -70,7 +70,7 @@
         },
         {
             "name": "formatTime",
-            "description": "Format the time according to the specified format. The pattern of the formatter contains of hh(hour), mm(minute), ss(second) and delimiter, they are case insensitive, such as: hh-mm-ss or hh:mm:s",
+            "description": "Format the date according to the specified format. The format uses hh(hour), mm(minute), ss(second), they are case insensitive",
             "example": "datetime.formatTime（\"10:11:05.00000\", \"hh-mm-ss\") => 10-11-05",
             "args": [
                 {