Cmake updates

[K20shores]

• Only install the project when it is top level
• Add library alias
• Use cmake to configure the .VERSION file and let cmake control the versions.
• Updates to cmake 3.0 (this is the version that lets you set the project version and version variables in the project command)

This encompasses everything in #527 , #528, #529 so those can be closed.

[K20shores]

@jacobwilliams I have merged all three of my previous PRs into this one. Also, cmake now generates the .VERSION file so that the documentation still works

[jacobwilliams]

Thank you! I'll look at it as soon as I get a chance!