CSHARP-952: removed AllowPartiallyTrustedCallers and removed all SecurityXXX attributes.
moved psake-ext.ps1 out of tools and into build folder.
renamed psake-ext to build-helpers.
CSHARP-573: changed the machine part of an ObjectId to come from the hash code of the machine name instead of the MD5 hash, which was causing issues in FIPS compliant organizations.
upgraded Nunit to 2.6.3 from 2.6.1.