Use preReleaseVersion for Akka.Cluster

When building:
    build.cmd Nuget
the package name for cluster will be like this:
   Akka.Cluster.0.6.5-pre1410160612

The numbers after pre are the UTC date and time on the format "yyMMddHHmm" to get an increasing version number of the prerelease package (as long as you build the next version the minute after).

This commit also makes sure that when building pre-release versions of all packages using
    build.cmd Nuget nugetprerelease=dev
the name of Akka.Cluster package use the specified prefix. In this example the name will be:
   Akka.Cluster.0.6.5-dev1410160612
Merge pull request #477 from HCanber/akka-cluster-packagename

Use preReleaseVersion for Akka.Cluster
Akka.NET v0.7
Actor PreRestart(): wrong message and sender #456
Updated release notes to mention Akka.TestKit
Merge pull request #481 from rogeralsing/wrong-message-and-sender-456

FIX: Actor PreRestart(): wrong message and sender #456
Merge pull request #479 from Aaronontheweb/dev

Akka.NET v0.7
changed build.fsx to add Akka.Remote NuGet dependency to Akka.Cluster
Moved things from 0.6.5 to 0.7 release notes.

The ones in 0.6.5 were ment to be used in the release-notes for vNext
Add a new 0.7.1 entry in RELEASE_NOTES

This is a placeholder for next version. It might not be 0.7.1. This will enable us to add to RELEASE_NOTES during development.
Merge pull request #484 from Aaronontheweb/dev

changed build.fsx to add Akka.Remote NuGet dependency to Akka.Cluster
Merge pull request #487 from HCanber/fix-releasenotes

Fix releasenotes