vtkWeb: Refactor fetchObject(..) to use cached objects
vtkWeb: Refactor fetchObject(..) to use cached objects

Refactor fetchObject(..) to use a more straight forward cache
mechanisum. Moving much of the logic out of vtkReader.js.

Change-Id: Ib878dd70cb0a9427ba2015159b0ed34db0bc451f

ashray/VTK-EVM,candy7393/VTK,mspark93/VTK,msmolens/VTK,sumedhasingla/VTK,candy7393/VTK,sumedhasingla/VTK,gram526/VTK,hendradarwin/VTK,demarle/VTK,SimVascular/VTK,SimVascular/VTK,hendradarwin/VTK,johnkit/vtk-dev,mspark93/VTK,msmolens/VTK,keithroe/vtkoptix,berendkleinhaneveld/VTK,sumedhasingla/VTK,sumedhasingla/VTK,demarle/VTK,sankhesh/VTK,ashray/VTK-EVM,candy7393/VTK,msmolens/VTK,johnkit/vtk-dev,jmerkow/VTK,demarle/VTK,mspark93/VTK,sankhesh/VTK,jmerkow/VTK,msmolens/VTK,keithroe/vtkoptix,ashray/VTK-EVM,ashray/VTK-EVM,SimVascular/VTK,sumedhasingla/VTK,msmolens/VTK,jmerkow/VTK,sankhesh/VTK,demarle/VTK,keithroe/vtkoptix,candy7393/VTK,keithroe/vtkoptix,gram526/VTK,berendkleinhaneveld/VTK,ashray/VTK-EVM,sankhesh/VTK,sumedhasingla/VTK,sankhesh/VTK,hendradarwin/VTK,keithroe/vtkoptix,ashray/VTK-EVM,msmolens/VTK,sankhesh/VTK,demarle/VTK,ashray/VTK-EVM,candy7393/VTK,SimVascular/VTK,SimVascular/VTK,keithroe/vtkoptix,hendradarwin/VTK,gram526/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,hendradarwin/VTK,gram526/VTK,berendkleinhaneveld/VTK,demarle/VTK,SimVascular/VTK,msmolens/VTK,mspark93/VTK,johnkit/vtk-dev,jmerkow/VTK,mspark93/VTK,hendradarwin/VTK,candy7393/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,ashray/VTK-EVM,sumedhasingla/VTK,johnkit/vtk-dev,demarle/VTK,gram526/VTK,keithroe/vtkoptix,mspark93/VTK,johnkit/vtk-dev,jmerkow/VTK,SimVascular/VTK,jmerkow/VTK,sankhesh/VTK,sumedhasingla/VTK,sankhesh/VTK,hendradarwin/VTK,candy7393/VTK,SimVascular/VTK,msmolens/VTK,berendkleinhaneveld/VTK,gram526/VTK,gram526/VTK,mspark93/VTK,demarle/VTK,berendkleinhaneveld/VTK,mspark93/VTK,jmerkow/VTK,gram526/VTK,johnkit/vtk-dev,johnkit/vtk-dev,candy7393/VTK