Update GoogleTest to 1.8.0 release
Update GoogleTest to 1.8.0 release

Fix passing of arguments to GoogleTest project. Only build and install
GTest and not GMock.

Change-Id: I3b3d415a1b8c7a1ff6f3f9065fa6e5f0d8b2f630

kaspermarstal/SimpleElastix,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,kaspermarstal/SimpleElastix,InsightSoftwareConsortium/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,kaspermarstal/SimpleElastix,richardbeare/SimpleITK,SimpleITK/SimpleITK,kaspermarstal/SimpleElastix,blowekamp/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,blowekamp/SimpleITK,kaspermarstal/SimpleElastix,richardbeare/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,blowekamp/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,richardbeare/SimpleITK,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,richardbeare/SimpleITK