JCLOUDS-171: Fixed NPE when destroying nodes in Abiquo

There was a race condition when destroying a node in Abiquo
using the ComputeService: jclouds performed the active wait
until the node was in state TERMINATED, and used the transformation
functions to convert an Abiquo VirtualMachine to a NodeMetadata. If the
node was effectively deleted during this transformation, a NPE
was raised. This is because there are a couple of API calls that are
executed in that transformation to retrieve all information required
to build the NodeMetadata.

To prevent this, the AbiquoComputeServiceAdapter will block until the
node has been actually deleted instead of delegating that to jclouds.
This way there is no need to run the transformation functions that had
the race condition.
Use ComputeService timeouts to avoid blocking forever
JCLOUDS-182: List all virtual machines in Abiquo

Since Abiquo 2.4, all virtual machines for a user can be
retrieved in a single API call.

This change removes the strategy that fetched the details
of all virtual appliances first (to then get the virtual
machines in them), and updates the CloudService to use the
single API call.
JCLOUDS-188: Include pagination parameters in Abiquo VirtualMachineTemplateOptions

Modified the Abiquo VirtualMachineTemplateOptions builder to inherit from
the BaseFilterOptionsBuilder so it can accept pagination parameters.
Also superseded the OrderBy enum by a simple String, to avoid hardcoding
the fields that are suitable to be sorted.
The OrderBy enum has been removed and the FilterOptions class moved to a
more convenient package.
JCLOUDS-208: The datacenter link has been added to the Limits object construction.

This link is used in the 2.4 version of the Abiquo API to establish a relation
between an enterprise and the datacenter it is restricted to.
CloudSigma v2 API and Providers.