Convert VMWareSystem to psphere

Based in-part on @apagac's work in #893, this switches VMWareSystem over to psphere and removes the requirement for pysphere.

Unfortunately, I can't get `deploy_template` to work, so I'm putting this up as a WIP for anyone (@psav? @mfalesni?) to look at, and hopefully get `deploy_template` working well.

The issue I was running into is a VimFault:
```python
from utils import providers, mgmt_system
p = providers.provider_factory('vsphere55')
p.deploy_template('fedora19', 'clonetest', resourcepool='vCenter')
```

```
Server raised fault: '
Error parsing string  as enum type VirtualMachineRelocateTransformation

while parsing serialized value of type vim.vm.RelocateSpec.Transformation
at line 1, column 490

while parsing property "transform" of static type VirtualMachineRelocateTransformation

while parsing serialized DataObject of type vim.vm.RelocateSpec
```

The two spaces in the first line "Error parsing string>>  <<as enum" indicate that the string that should be there (which is "trim", according to my code) isn't making its way through the SOAP plinko machine into the request.