Fluentmigrator.Runner support for multiple assemblies at a time

[MikeBagos]

Added support for FluentMigrator.Runner to proccess multiple assemblies at a time, passed as a collection of MigrationAssemblyInfo packages. Kept compatibility with older code as existing constructors were replaced to point to new constructors.

Also fixed the test, which pass. Extensive test were not created/performed.

[nslowes]

This will be useful for scenarios I've been thinking about with Profiles contained in separate assemblies from the main Migrations

[daniellee]

Do users of FluentMigrator need the ability to apply migrations from multiple assemblies with only one VersionInfo table? Sounds like an edge case to me. This is very similar to #187.

[ghost]

Pretty useful ability for modular applications. Thumbs up for this feature.

[tommarien]

Should be closed by pulling #467