Updated the default mapping of Int64 to NUMBER(19,0) to match the default type mapping used by Oracle.

See Table 3-4: Mapping of Oracle Data Types and EDM Types (http://docs.oracle.com/cd/E11882_01/win.112/e18754/featLINQ.htm)
Allow data to be inserted using a dictionary and refactor existing code closes #458
Update MySqlTypeMap.cs

version 1.1.2 causes error when migrating 'versioninfo' table by adding a 'description' column on MySQL database.
This error caused by method 'Up' in 'VersionDescriptionMigration' class. The method calls .AsString(int.MaxValue) which is beyond 
definition in MySqlTypeMap class
Lazy loading migrations
added LazyLoader;
Added Constraint("name").Exists() to SchemaTable syntax
Fixes solution project change
Add tests for constraint schema check
Merge pull request #1 from matthewdunsdon/ConstraintExists

Constraint exists work fixups
Added UnitTest for Index Exists
Makes tests for Sql Server sequences rollback on fail

If not Sql Server 2012 is enabled in the IntegrationTestOptions then
ignore these tests.

If the one of the tests fails then rollback the transaction. Otherwise
a schema can be created that messes up the other tests. The basic
principle is that a test should be repeatable and should cleanup after
itself.
Use VARCHAR(255) for Firebird string default

The Firebird generator was using BLOB SUB_TYPE TEXT as the default type
for AsString(). I've changed it to use VARCHAR(255) instead since
this is more likely what is actually desired.

column.AsString() => VARCHAR(255)
column.AsString(100) => VARCHAR(100)
column.AsString(10000000) => BLOB SUB_TYPE TEXT
Use more accurate max text size

Firebird can handle up to 32GB but we're limited to int.MaxValue.
Improve text size comment
Ignore Firebird Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.
Ignore MySql Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.
Ignore Jet Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.
Ignore Oracle Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.
Ignore Postgres Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.
Ignore Oracle Processor Integration tests if not enabled in test config

Checks the IntegrationTestOptions if enabled otherwise it ignores the
tests.