[Feature] Add cutout and lighting (open-mmlab#909)

* add cutout

* add adjust_lighting

* minor fix

Bump version to v1.2.7 (open-mmlab#842)

Bump version to v1.2.6 (open-mmlab#799)

Bump version to v1.2.5 (open-mmlab#770)

bump version to v1.2.4 (open-mmlab#764)

bump version to 1.2.3 (open-mmlab#761)

bump version to v1.2.2 (open-mmlab#714)

* bump version to 1.2.1

* update installation table in readme

* break new line

* del mmcv upper bound for old installation

* reminder on latest

* bump version to v1.2.2

bump version to 1.2.1 (open-mmlab#672)

bump version to 1.2.0 (open-mmlab#644)

bump version to 1.1.6 (open-mmlab#629)