Remove empty strings from source request JSON

A ```defaultDateFormat``` of ```""``` means the format is being set to the empty string, not that there is no ```defaultDateFormat``` specified. 

This commit:
- Removes unnecessary transient fields (```alive```, ```status```)
- Removes incorrect configurations (empty ```description```, ```defaultDateFormat```)

templates/default/sumo.json.erb

@@ -4,15 +4,11 @@
         {
             "name": "Messages",
             "sourceType": "LocalFile",
-            "alive": true,
-            "status": "",
             "automaticDateParsing": true,
             "multilineProcessingEnabled": false,
             "useAutolineMatching": true,
             "forceTimeZone": false,
-            "defaultDateFormat": "",
             "timeZone": "UTC",
-            "description": "",
             "filters": [],
             "category": "OS/Linux/System",
             "blacklist": [],
@@ -21,15 +17,11 @@
         {
             "name": "Secure",
             "sourceType": "LocalFile",
-            "alive": true,
-            "status": "",
             "automaticDateParsing": true,
             "multilineProcessingEnabled": false,
             "useAutolineMatching": true,
             "forceTimeZone": false,
-            "defaultDateFormat": "",
             "timeZone": "UTC",
-            "description": "",
             "filters": [],
             "category": "OS/Linux/Security",
             "blacklist": [],
@@ -38,15 +30,11 @@
         {
             "name": "Syslog File",
             "sourceType": "LocalFile",
-            "alive": true,
-            "status": "",
             "automaticDateParsing": true,
             "multilineProcessingEnabled": false,
             "useAutolineMatching": true,
             "forceTimeZone": false,
-            "defaultDateFormat": "",
             "timeZone": "UTC",
-            "description": "",
             "filters": [],
             "category": "OS/Linux/System",
             "blacklist": [],