Add ability to filter in `slcli account billing-items`

[allmightyspiff]

We should be able to filter by Ordered By, Category Code and Create Date in this command.

$> slcli account billing-items
                                                                                         Billing Items
┌────────────┬─────────────┬─────────┬────────────────────────────────────┬─────────────────┬───────────────────────────────────────────────────────┬─────────────────────────────────────────┐
│     Id     │ Create Date │  Cost   │ Category Code                      │   Ordered By    │ Description                                           │                  Notes                  │
├────────────┼─────────────┼─────────┼────────────────────────────────────┼─────────────────┼───────────────────────────────────────────────────────┼─────────────────────────────────────────┤
│  19388750  │ 2014-02-22  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  19492772  │ 2014-02-23  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  19566702  │ 2014-02-24  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  23458576  │ 2014-04-15  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  23909194  │ 2014-04-21  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  24798220  │ 2014-05-01  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  25296564  │ 2014-05-08  │    0    │ guest_storage                      │       IBM       │ Image Template Storage                                │                  None                   │
│  26962680  │ 2014-05-29  │    0    │ public_storage                     │       IBM       │ Public Image Storage                                  │                  None                   │