add framework illustration in Bottlenecks docs

JIRA: BOTTLENECK-88

changes:

1. add framework image in platformoveriew/introduction.rst to make
the Bottlenecks docs more user friendly

2. image name in platformoveriew/introduction.rst is not correctly
writed, correct it as Framework_Setup.png

3. correct the image width error

4. correct image path

5. change the illustration to Rubbos introduction section as commented

6. move the illustration in top-level directory as suggested

7. add brief decription of the illustration

Change-Id: Id86b813fa6e0a68349de60bb294b1cef43484a9a
Signed-off-by: yuyang <Gabriel.yuyang@huawei.com>