Integrated publisher policy into build

- Publisher policy creation can now be done via the csproj,
  with the PublisherPolicy target
- Deleted old batch file method
- Integrated new method into Npgsql, Npgsql.EntityFramework and
  Npgsql.EntityFrameworkLegacy
- Updated version numbers

Note: we still have to manually manage bumping the versions,
need to find a proper solution for this
Exclude publisher policy DLL from nuget
Added missing nuget dependency to EntityFrameworkLegacy
Added nuget dependencies for EntityFramework

The two Npgsql.EntityFramework nugets were missing
dependencies on EntityFramework itself, added those.
Added nuget EFProvider installation

Added nuget Powershell installation script for
Npgsql.EntityFramework, which adds the Npgsql
EF provider into the project's App.config, as
recommended here:
http://entityframework.codeplex.com/wikipage?title=Rebuilding%20EF%20providers%20for%20EF6

Note that this wasn't done for legacy EF
Added missing RootNamespace in csprojs
Added EF6 ConnectionFactory class
Fix loading of embedded NpgsqlMetaData.xml

Required by the introduction of <RootNamespace> in
6e3256916966b43780ae1387c236fd12e4cbab1e