Merge pull request #1865 from agrare/add_documentation_allocated_disk_storage

Add documentation on increasing cloned vm disk size

(cherry picked from commit 12ab231)

Author: Fryguy

api/appendices/advanced_provisioning.md

@@ -12,6 +12,8 @@ provisioning via /api/provision\_requests.
 
   - [Defining new Disks](#defining-new-disks)
 
+  - [Increasing the template disk size](#increasing-the-template-disk-size)
+
   - [Cloning Type](#cloning-type)
 
   - [Limit Template Selection](#limit-template-selection)
@@ -86,6 +88,18 @@ Example:
 "diskscsi1.backing.diskmode" : "independent_persistent"
 ```
 
+### Increasing the template disk size
+
+The `allocated_disk_storage` attribute allows for the first disk on a VM to be increased in size
+after the clone operation is complete.  This is only supported for templates with 1 disk.
+The attribute's unit is gigabytes.
+
+This is supported by the VMware vSphere provider.
+
+```json
+allocated_disk_storage: 10
+```
+
 ### Cloning Type
 
 This attribute sets the type of cloning request, either clone to vm or