New tool to store SQL connection configs locally (#218)

* added a new tool to store SQL connections locally. Modified the peek definition tests to create test database before running test


* fixed failing test QueryExecutionPlanInvalidParamsTest

* Fixes based on code review comments

* fixed failing test GetSignatureHelpReturnsNotNullIfParseInfoInitialized

test/Microsoft.SqlTools.ServiceLayer.PerfTests/Tests/Common.cs

@@ -7,6 +7,9 @@ namespace Microsoft.SqlTools.ServiceLayer.PerfTests
 {
     public class Common
     {
-        public const string PerfTestDatabaseName = "SQLToolsCrossPlatPerfTestDb";
+        /// <summary>
+        /// The name of the test db to be used for performance tests. Prefix "keep" is used so the db doesn't get deleted by cleanup jobs
+        /// </summary>
+        public const string PerfTestDatabaseName = "keep_SQLToolsCrossPlatPerfTestDb";
     }
 }