Grid Enhancement - Show Message when Loading Data

Sometimes when we draw a grid, the data is not ready and it's a time-consuming
task for back-end, so the user will expect that the grid is drawn there, and a
"loading" message is on top of the grid while loading data.

  In this patch, we make this enhancement. Meanwhile, we introduce a "loading"
icon which is made based-on Kimchi logo.

Signed-off-by: Hongliang Wang <hlwang@linux.vnet.ibm.com>