Bazel: Make manifest entries consistent with Maven build

Add Implementation-Vendor and Gerrit-ApiType, and modify
Implementation-Name to be the same as defined in the Maven build.

Omit the Implementation-Version, since this is also not defined in
any of the other bazel-built plugins and will cause extra work when
updating the API version.

Change-Id: I8ab57e8994bd581822ee596edc8d78be4558f452
diff --git a/BUILD b/BUILD
index 658f3da..ba18e42 100644
--- a/BUILD
+++ b/BUILD
@@ -10,9 +10,11 @@
     name = "slack-integration",
     srcs = glob(["src/main/java/**/*.java"]),
     manifest_entries = [
+        "Gerrit-ApiType: plugin",
         "Gerrit-PluginName: slack-integration",
-        "Implementation-Title: slack-integration plugin",
+        "Implementation-Title: Slack Integration",
         "Implementation-URL: https://gerrit-review.googlesource.com/#/admin/projects/plugins/slack-integration",
+        "Implementation-Vendor: Cisco Systems, Inc.",
     ],
     resources = glob(["src/main/resources/**/*"]),
 )