Add local Maven configuration using .mvn/

- Adding extension for the Takari Smart Builder which provides better
  parallelization of the build

- Adding extension for concurrent local repository access which is
  required when using the Smart Builder

- Add configuration to enable the Smart Builder and use 8 threads

- Add configuration to set the JVM -Xmx option

- Add .mvn/timing.properties to .gitignore

.gitignore

@@ -21,3 +21,4 @@ benchmark_outputs
 *.class
 .checkstyle
 *-local.yaml
+.mvn/timing.properties 

.mvn/extensions.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<extensions>
+  <extension>
+    <groupId>io.takari.maven</groupId>
+    <artifactId>takari-smart-builder</artifactId>
+    <version>0.4.0</version>
+  </extension>
+  <extension>
+    <groupId>io.takari.aether</groupId>
+    <artifactId>takari-concurrent-localrepo</artifactId>
+     <version>0.0.7</version>
+  </extension>
+</extensions>

.mvn/jvm.config

@@ -0,0 +1 @@
+-Xmx8192m 

.mvn/maven.config

@@ -0,0 +1,2 @@
+-T 8
+--builder smart