Added transaction handling to Jet, and corrected some typos
Removed unnecessary SupportsTransactions property and corrected another typo
Readding check if transaction exists to firebird's rollback override
Implement Reverse function for CreateConstraintExpression
Don't exclude firebird from CanCreateUniqueConstraint() test
Integration tests for autoreverse CreateConstraint

 - With and without schema
Closes #379 pull request from concept-hf/firebird-tpmreview
Refactored name of migration into MigrationInfo
Introduced IMigrationScope to allow scopes to be used outside of runnercontext and to prepare for transaction-per-session runner option

Created NonAttributedMigrationToMigrationInfoAdapter to allow removal of duplicate code in migrationrunner up/applymigrationup etc
Moved all IMigrationInfo implementations in separate files

Added NonAttributedMigrationInfoAdapter
Added Imigrationinfo extension method
Cleanup duplication of up/applymigrationup closes #381
Added transaction-per-session option to all runners

Added option to runnercontext
First dry run closes #380
Merge pull request #382 from dabide/jetfixes

Added transaction handling to Jet, and corrected some typos
Fixed spelling in JetGenerator
Add first Integration test for JetProcessor
Add more integration tests for JetProcessor
Spelling change
Add shorter tps switch in MigratorConsole

Additional switch for Transation per session for the command line.
Update README.textile
Refactor out validation from MigrationRunner

Create a new class called MigrationValidator that removes the internal
validation logic from the MigrationRunner.