Automate DKMS setup and source code updates

[rawenger]

I appreciate you setting all of this up @mkubecek, it's a total godsend. I recently had to automate the process of getting the VMware modules up and running through DKMS on a handful of machines, so I wrote this script. I've made some additions to make it as distro-agnostic as possible--let me know what you think. I've included an overview of the script's functionality at the top of dkms-setup.sh.

Edit to add: There should be no change in workflow to anyone not wishing to use DKMS.

========== COMMIT SUMMARY============

DKMS is a convenient framework for managing out-of-tree kernel modules, such as the ones in this repo. The dkms-setup.sh script will add the modules here (vmmon & vmnet, as of this writing) to the system's DKMS configuration, allowing them to be automatically rebuilt and resigned whenever the kernel is upgraded.

CHANGES:
- Add dkms.conf to .gitignore. The setup script will generate a dkms.conf file from the template dkms.conf.in.
- Add an optional override to the VM_UNAME variable in the Makefile. This is required to build for any non-running kernel (which DKMS will do whenever a new kernel is installed by the system package manager).

ADDITIONS:
- dkms-setup.sh: Shell script to manage setup and updates of the modules in this repo.
- dkms.conf.in: Template DKMS configuration file to be populated by the setup script.

[vasi]

This is a great idea, but it doesn't work quite right for me. We checkout a different branch name, and then attempt to process dkms.conf.in, but it's no longer present!

Obviously that'd be fine if we integrated dkms.conf.in to all branches, but it makes it a bit hard to test.

[vasi]

I think just moving the dkms.conf generation above the branch-switch should fix this.

[rawenger]

Fixed! Good catch @vasi