Allow configuration of external module dependency locations
Allow configuration of external module dependency locations

Teach the vtk_module_export_code_find_package macro to check for a
VTK_INSTALL_FIND_PACKAGE_<name>_DIR variable to configure the default
location of <name>_DIR to be reported to applications.  Allow the
variable to be set to a false value to disable the default.  This will
allow module dependencies on external packages such as Qt5 to be
configured for redistributable/relocatable packages.

Also allow applications to set <name>_DIR themselves before finding
VTK so that they can override the VTK-provided default location.

Change-Id: I0e452fb02f371636ec3a04954a99e33c7193f77a

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