Add target id to export

Allows the intellij pants plugin to find the classpath based on the target id, without computing the target id in the plugin.

Testing Done:
Green: https://travis-ci.org/pantsbuild/pants/builds/100217667

Bugs closed: 2764

Reviewed at https://rbcommons.com/s/twitter/r/3291/

src/python/pants/backend/project_info/tasks/export.py

@@ -37,7 +37,7 @@
 
 
 # Changing the behavior of this task may affect the IntelliJ Pants plugin.
-# Please add fkorotkov, tdesai to reviews for this file.
+# Please add tdesai to reviews for this file.
 class ExportTask(IvyTaskMixin, PythonTask):
   """Base class for generating a json-formattable blob of data about the target graph.
 
@@ -56,7 +56,7 @@ class ExportTask(IvyTaskMixin, PythonTask):
   #
   # Note format changes in src/python/pants/docs/export.md and update the Changelog section.
   #
-  DEFAULT_EXPORT_VERSION = '1.0.4'
+  DEFAULT_EXPORT_VERSION = '1.0.5'
 
   @classmethod
   def subsystem_dependencies(cls):
@@ -187,6 +187,7 @@ def get_target_type(target):
         'targets': [],
         'libraries': [],
         'roots': [],
+        'id': current_target.id,
         'target_type': get_target_type(current_target),
         'is_code_gen': current_target.is_codegen,
         'pants_target_type': self._get_pants_target_alias(type(current_target))

tests/python/pants_test/backend/project_info/tasks/test_export.py

@@ -197,7 +197,7 @@ def test_without_dependencies(self):
 
   def test_version(self):
     result = self.execute_export_json('project_info:first')
-    self.assertEqual('1.0.4', result['version'])
+    self.assertEqual('1.0.5', result['version'])
 
   def test_sources(self):
     self.set_options(sources=True)
@@ -247,6 +247,7 @@ def test_jvm_target(self):
       'globs': {'globs': ['project_info/this/is/a/source/Foo.scala',
                           'project_info/this/is/a/source/Bar.scala']},
       'libraries': ['org.apache:apache-jar:12.12.2012', 'org.scala-lang:scala-library:2.10.5'],
+      'id': 'project_info.jvm_target',
       'is_code_gen': False,
       'targets': ['project_info:jar_lib', '//:scala-library'],
       'roots': [