CSHARP-934: reorganizing repository. Moved all source files into src folder and all build related files into build folder.

moved GlobalAssemblyInfo.cs and TestEnvironment.cs into shared folder.
CSHARP-934: adjusting build script to accomodate new repository structure.
CSHARP-616: removed strong naming and removed the keys.
 upgraded projects to VS2013
CSHARP-625: changed projects to target .NET 4.5. Will add in compilation constants for 4.5 specific features to allow us to target 4.0 during builds.
CSHARP-625: build script now builds both .NET 4.0 and .NET 4.5. Still need to update the docs project and the installer project.
CSHARP-625: upgraded installer to handle both .NET 4.0 and .NET 4.5 binaries.
fixed regex for finding build number.
CSHARP-934: renamed test assemblies to *.Tests.
CSHARP-934: changed default namespace and namespaces for all test files.
Fixed unit tests that were affected by the namespace changes.
BsonDocument no longer implements IBsonSerializable.
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.
Fixed nunit.exe.config to support setting breakpoints when running unit tests.
CSHARP-509: Remove superfluous Create methods.
CSHARP-509: Change how BsonValue Create methods handle C# null.