Cleanup of MigrationRunnerTests

Moved tests marked Ignore to MigrationLoaderTests. I had to change
the implementation of the tests to get them working with the existing
MigrationLoader code.
Add validation step to MigrationRunner

Moved ApplyConventions as they have to be applied before the validation
step. Do that separately in its own loop together with validation and
not in the main ExecuteExpressions loop. This uses the existing
validations that already exist for expressions that have implemented the
ICanBeValidated interface.
Add Integration tests for Create Sequence

Add SequenceExists method to QuerySchema. Add test class for sequences.
Add integration tests for SqlServerProcessor and MigrationRunner.
This tests SqlServer2012, the next step is to test Postgres as well.
Fix validation rules for DeleteIndexExpression

Incorrect validation rule for DeleteIndexExpression caused migration to
fail when deleting an index.
Add more tests for validation in expressions

Need to check that all validation rules are correct so adding more
tests and double checking the rules that are already defined.
Add integration test for sequences for Postgres

Implemented SequenceExists in processor class as well.
Announce Postgres test has started
Add DeleteConstraintExpression tests

 - Changed validation message to standard message.
Fix and tests for DeleteForeignKeyExpression

There are two formats of this expression. Validated as incorrect for
one of the formats and would have broken a lot of migrations.
ApplyConventions had broken the reverse method so fixed that as well.
Add missing tests for DeleteSchema + Sequence Exp
Add Integration tests

 - Alter Column With Schema
- Alter Table With Schema
- Alter a tables schema
- Create Unique Constraint
Change AlterTable test

Test default constraint as well.
Integration tests for insert,update,delete data

Add tests for the insert, update and delete data expressions.
Add integration test for reversing create index
Add integrations without schema

Added copies of some of the tests except with no schema
defined for more comprehensive testing.
Merge branch 'validate' of https://github.com/daniellee/fluentmigrator into daniellee-validate
Merge pull request #363 from daniellee/validate

# By Daniel Lee
# Via Daniel Lee (1) and Tom Marien (1)
* daniellee-validate:
  Add integrations without schema
  Add integration test for reversing create index
  Integration tests for insert,update,delete data
  Change AlterTable test
  Add Integration tests
  Add missing tests for DeleteSchema + Sequence Exp
  Fix and tests for DeleteForeignKeyExpression
  Add DeleteConstraintExpression tests
  Announce Postgres test has started
  Add integration test for sequences for Postgres
  Add more tests for validation in expressions
  Fix validation rules for DeleteIndexExpression
  Add Integration tests for Create Sequence
  Add validation step to MigrationRunner
  Cleanup of MigrationRunnerTests