We've been using a certain pattern for the Windows .msi for a long
time but the build output used a different name which we simply
manually renamed before publishing.
Since we want to automate as much as possible we can change the
build to produce the correct name right away.
* [ci] Add Jenkins pipeline script for building OSX and Windows packages
This replaces the current Jenkins freestyle jobs.
We no longer need the signing inside of the MacSDKRelease profile
since we're now signing on a separate service and having the signing
certificates locally is discouraged anyway.
* [ci] Update embedded gtk-sharp in Windows msi to 2.12.45
This matches what we ship on www.mono-project.com