[SPARK-3777] Display "Executor ID" for Tasks in Stage page

Now the Stage page only displays "Executor"(host) for tasks. However, there may be more than one Executors running in the same host. Currently, when some task is hung, I only know the host of the faulty executor. Therefore I have to check all executors in the host.

Adding "Executor ID" in the Tasks table. would be helpful to locate the faulty executor. Here is the new page:

![add_executor_id_for_tasks](https://cloud.githubusercontent.com/assets/1000778/4505774/acb9648c-4afa-11e4-8826-8768a0a60cc9.png)

Author: zsxwing <zsxwing@gmail.com>

Closes #2642 from zsxwing/SPARK-3777 and squashes the following commits:

37945af [zsxwing] Put Executor ID and Host into one cell
4bbe2c7 [zsxwing] [SPARK-3777] Display "Executor ID" for Tasks in Stage page

(cherry picked from commit 446063eca98ae56d1ac61415f4c6e89699b8db02)
Signed-off-by: Andrew Or <andrewor14@gmail.com>
[SPARK-3829] Make Spark logo image on the header of HistoryPage as a link to HistoryPage's page #1

There is a Spark logo on the header of HistoryPage.
We can have too many HistoryPages if we run 20+ applications. So I think, it's useful if the logo is as a link to the HistoryPage's page number 1.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2690 from sarutak/SPARK-3829 and squashes the following commits:

908c109 [Kousuke Saruta] Removed extra space.
00bfbd7 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-3829
dd87480 [Kousuke Saruta] Made header Spark log image as a link to History Server's top page.

(cherry picked from commit b69c9fb6fb048509bbd8430fb697dc3a5ca4fe59)
Signed-off-by: Andrew Or <andrewor14@gmail.com>