Improved OpenNebula support

This patch improves Fog's OpenNebula support in a number of ways:
Better NIC support in VM templates
Better ability to tune number of CPUs and memory
Ability to add/remove entries from a VM template's context section
Ability to add/remove entries from a VM template's user variables
Improved filtering for templates and NICs
Improved OpenNebula support

This patch improves Fog's OpenNebula support in a number of ways:
Better NIC support in VM templates
Better ability to tune number of CPUs and memory
Ability to add/remove entries from a VM template's context section
Ability to add/remove entries from a VM template's user variables
Improved filtering for templates and NICs
Adding Tests and Mocks

Adding several test cases for flavors and updating network tests to
support new attributes.
Merge branch 'opennebula' of github.com:blackberry/fog into opennebula

Conflicts:
	fog.gemspec
	lib/fog/opennebula/models/compute/networks.rb
	lib/fog/opennebula/requests/compute/list_networks.rb
Merge remote-tracking branch 'upstream/master' into opennebula

Conflicts:
	fog.gemspec
Fixing merge conflict
Removing version dependency
Merge pull request #3255 from blackberry/opennebula

Improved OpenNebula support