Update paddle installation documents, make installation more simpler

[typhoonzero]

Update doc/getstarted/build_and_install to make installation steps more simple and clear, refined document structure is:

1. install using pip(supports linux and mac)
2. run with docker (supports linux, mac and windows)
   1. run book image
   2. run production image
   3. run docker with GPU
   4. run under windows under docker
3. build from source(supports linux and mac)
   1. build under docker
   2. build under differnet linux distributions
   3. build under mac OS
4. common build and install FAQs

[llxxxll]

Are you considering supporting windows?

[typhoonzero]

@llxxxll windows users can only run under docker, and may not be able to use GPU. Will add some tips for windows users also.

[llxxxll]

@typhoonzero ok~
and PaddlePaddle Mobile build&install ,do you want to add?

[typhoonzero]

Add to upper level of document index? Like:

1. getting started
   1. build and install
   2. run a demo
   3. run inference demo
2. paddle versions
3. training
4. inference
5. run on mobile
6. contributing
   ...

[luotao1]

As FAQ will make a document index (#4354), how about move "common build and install FAQs" into FAQ?

[typhoonzero]

@luotao1 Sure, definitely.

[NorthStar]

@abhinavarora can perhaps take on 3.iii, tagging him.