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.