Changed email model statuses in schema

- Renames were done as that suits how emails would be handled by the bulk email handler
- These statuses are only for internal representation of the state and don't represent what happens to emails delivery-wise
- There is no need for 'sent' status as emails are "never done" and stats wold be checked for stats field would be used to check on details of the status

core/server/data/schema/schema.js

@@ -385,8 +385,8 @@ module.exports = {
             type: 'string',
             maxlength: 50,
             nullable: false,
-            defaultTo: 'sending',
-            validations: {isIn: [['pending', 'sending', 'sent', 'failed']]}
+            defaultTo: 'pending',
+            validations: {isIn: [['pending', 'submitting', 'submitted', 'failed']]}
         },
         error: {type: 'string', maxlength: 2000, nullable: true},
         stats: {type: 'text', maxlength: 65535, nullable: true},

core/test/unit/data/schema/integrity_spec.js

@@ -19,7 +19,7 @@ var should = require('should'),
  */
 describe('DB version integrity', function () {
     // Only these variables should need updating
-    const currentSchemaHash = 'c4aac02dea06860a40932b1c128073e3';
+    const currentSchemaHash = 'ffc16afc9264ba20a0d8346387c163fb';
     const currentFixturesHash = 'b1787330f042f3954d73c43aa8bfa915';
 
     // If this test is failing, then it is likely a change has been made that requires a DB version bump,