Increased opam-friendliness

• re-add xenopsd plugin for xen-bugtool
• don't break when system gpg binary is upgraded
• set the right month for host crashdump records
• allow the location of the inventory file to read from xapi.conf

Much more configurable release

• revamped configuration handling and support of config file overrides
• prevent timeouts when collecting bugtools
• allow vCPU hotplug for HVM guests if feature-vcpu-hotplug is set
• improve cancellation of VM migration
• use busybox for DHCP on the host internal management network

Now builds with ocaml-4.00.1 again

• Several bugfixes
• Reinstate WLB code
• Fix build on ocaml 4.00.1

Now with vhd import support

We have

• vhd import
• migration bugfix
• lots of other bug fixes

Approach vector to 2.0

Merge pull request #1769 from djs55/smapiv2

Remove the hardcoded disabling of ballooning for dom0