Add .editorconfig file

My default settings differ from this project's preferred settings. VS2017
supports .editorconfig files, so hopefully this will help keep everybody
consistent.

.editorconfig

@@ -0,0 +1,3 @@
+[*]
+end_of_line = crlf
+indent_style = tab

SourcetrailExtension.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26730.8
+VisualStudioVersion = 15.0.26730.16
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SourcetrailExtension", "SourcetrailExtension\SourcetrailExtension.csproj", "{A585A530-E120-4C74-934E-D57ED12A7DA9}"
 	ProjectSection(ProjectDependencies) = postProject
@@ -31,6 +31,7 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SourcetrailExtensionUtility
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{7298A53A-50A0-404A-B0C8-B408FE8AF2FB}"
 	ProjectSection(SolutionItems) = preProject
+		.editorconfig = .editorconfig
 		.gitignore = .gitignore
 		CHANGELOG.md = CHANGELOG.md
 		IntegrationTests.testsettings = IntegrationTests.testsettings
@@ -39,9 +40,6 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 	EndProjectSection
 EndProject
 Global
-	GlobalSection(Performance) = preSolution
-		HasPerformanceSessions = true
-	EndGlobalSection
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
 		Release|Any CPU = Release|Any CPU
@@ -93,4 +91,7 @@ Global
 	GlobalSection(Performance) = preSolution
 		HasPerformanceSessions = true
 	EndGlobalSection
+	GlobalSection(Performance) = preSolution
+		HasPerformanceSessions = true
+	EndGlobalSection
 EndGlobal