Splits a batched SQL string into separate statements for SQLServerCE

SQLServerCE can not handled batched SQL statements, which makes it
difficult to use SQL scripts in a migration. This commit is a naive
implementation that works in some cases.
Added SQLServer specific unicode insert.
Merge branch 'master' into pr366

Conflicts:
	src/FluentMigrator.Runner/Processors/SqlServer/SqlServerCeProcessor.cs
3 tests for #366

Tests executing multiple statements for SqlServerCE
Merge pull request #366 from redsolo/master
Merge branch 'master' into pr378
Move ExplicitUnicodeString to core namespace

 - Otherwise, the user has to introduce an extra using:
Fluentmigrator.Model which is unneccesary.
Merge pull request #378 from Ashthos/master
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