Add ability to change default quota

[yong sheng gong]

Problem:
Currently, the default quota is defined in configure file of neutron server: neutron.conf.
admin isnot able to change it via API.

other service nova, cinder can do it by, for example 'nova quota-class-update --instances -1 --cores -1 default'

expectation:
implement an API to let admin change the default quota. By client, it maybe:
neutron quota-class-update --ports xx --networks yy --security-groups --zz default

[Victor Morales (electrocucaracha)]

The way to change those values is thru the OSC,:

$ openstack project list
+----------------------------------+--------------------+
| ID | Name |
+----------------------------------+--------------------+
| 49f3e83f85354ee3a0abadcf1e35c9f4 | demo |
| 5a46e724e04d41beaf365d7148f8f465 | invisible_to_admin |
| 6ebf8c5aadea49fdb6222eae1e1639c0 | admin |
| 82533c3679a747189c401d42345f75b2 | service |
| a0c776bc0aa645a6845cd7919512ed01 | alt_demo |
+----------------------------------+--------------------+

$ openstack quota set --secgroups 15 49f3e83f85354ee3a0abadcf1e35c9f4

$ openstack quota show 49f3e83f85354ee3a0abadcf1e35c9f4
+-----------------------+----------------------------------+
| Field | Value |
+-----------------------+----------------------------------+
| backup-gigabytes | 1000 |
| backups | 10 |
| cores | 20 |
| fixed-ips | -1 |
| floating-ips | 50 |
| gigabytes | 1000 |
| gigabytes_lvmdriver-1 | -1 |
| health_monitors | None |
| injected-file-size | 10240 |
| injected-files | 5 |
| injected-path-size | 255 |
| instances | 10 |
| key-pairs | 100 |
| l7_policies | None |
| listeners | None |
| load_balancers | None |
| location | None |
| name | None |
| networks | 10 |
| per-volume-gigabytes | -1 |
| pools | None |
| ports | 50 |
| project | 49f3e83f85354ee3a0abadcf1e35c9f4 |
| project_id | None |
| properties | 128 |
| ram | 51200 |
| rbac_policies | 10 |
| routers | 10 |
| secgroup-rules | 100 |
| secgroups | 15 |
| server-group-members | 10 |
| server-groups | 10 |
| snapshots | 10 |
| snapshots_lvmdriver-1 | -1 |
| subnet_pools | -1 |
| subnets | 10 |
| volumes | 10 |
| volumes_lvmdriver-1 | -1 ...