OP-105 Basic scaffolding of asset upload in asset picker

[skip ci]
OP-105 Fixing alignment of the dropzone icons (should have been centered)

[skip ci]
OP-105 tweaks to the asset upload dropzone layout when in modal dialog

[skip ci]
Revert "OP-105 tweaks to the asset upload dropzone layout when in modal dialog"

This reverts commit 7780b818e671f3cc805946c255e9bb6a5e88d8c6.
Revert "OP-105 Fixing alignment of the dropzone icons (should have been centered)"

This reverts commit 52f0f7109e4f120b3dfebbccb1a7b489292b4c68.
Revert "OP-105 Basic scaffolding of asset upload in asset picker"

This reverts commit 558b429030814911e0fce23f2da79446bc83444c.