Windows Support (Experimental) (#75)

* Windows basic support

* getting_started updated for Windows.

* add experimental

* install.md restructured to seperate Windows & Linux.

* fix problems in install.md

* fix mmcv version problem.

* Fix fastscnn resize problems. (#82)

* Fix fast_scnn resize problems

* Fix fast_scnn resize problems 1

* Fix fast_scnn resize problems 2

* test for pascal voc

* [Doc] Add annotaion format note (#77)

* update pytorch version to 1.6.0 in install.md

* del fastscnn_pascal config

* del create_symlink=True

* Merge instructions for Linux & Windows

* mmcv version updated

* redundant newline deleted

* Update docs/install.md

Co-authored-by: Jerry Jiarui XU <xvjiarui0826@gmail.com>

* Update docs/install.md

Co-authored-by: Jerry Jiarui XU <xvjiarui0826@gmail.com>

Co-authored-by: Jerry Jiarui XU <xvjiarui0826@gmail.com>