Split dialects & drivers into separate projects which reference the relevant client library, MicroLite will only support MS Sql Server in the core assembly

[TrevorPilley]

The idea here will be that the core MicroLite library will contain the Session API and support for MS SQL Server along with all the other classes and interfaces for things like listeners, type converters etc. We will then have specific projects which reference MicroLite and the relevant .NET library for their specific database type e.g.:

• MicroLite.Database.FirebirdSql
• MicroLite.Database.MySql
• MicroLite.Database.PostgreSql
• MicroLite.Database.SQLite

[TrevorPilley]

Given the size of this and since it's effectively a breaking change, I'm pushing it back out to 7.0