Issue #341: Getting CCNet to build with mono under unix

Hi,

This PR addresses http://www.cruisecontrolnet.org/issues/341.

There are three things:

* NAnt needs config for "mono-4.5" since the upgrade to .Net 4.5. This is a copy of the mono-4.0 config with a couple of replacements to target 4.5.
* BuildEvents need to have unix equivalents where there are windows specific commands
* When building on case-sensitive file systems (so linux, but not windows / OS X) paths need to have correct casing.

To build the solution having made these changes I also had to remove the `CCNet.VBDemos.Plugin` from the `.sln` file. I'm not sure whether this is expected to build or not, so I'm omitting the change from this PR. Aside from that I am able to build the solution using NAnt or xbuild on a ubuntu 14.04 VM.

Cheers,
Rich