ENH: use HTTPS for external dependencies on github

googletest git repository was using the SSH protocol
instead of HTTPS, which requires users to add an
ssh_key on github.com.

We switch all those external projects to HTTPS protocol,
but keep the ones hosted by ourselves on gitlab.kitware.com
in SSH since we might be contributing back to those
during development.

CMake/External/External_GoogleTest.cmake

@@ -3,7 +3,7 @@
 #-----------------------------------------------------------------------------
 include(imstkAddExternalProject)
 imstk_add_external_project( GoogleTest
-  GIT_REPOSITORY git@github.com:google/googletest.git
+  GIT_REPOSITORY https://github.com/google/googletest.git
   GIT_TAG release-1.8.0
   INSTALL_COMMAND ${SKIP_STEP_COMMAND}
   CMAKE_ARGS

CMake/External/External_PThreads.cmake

@@ -3,7 +3,7 @@
 #-----------------------------------------------------------------------------
 include(imstkAddExternalProject)
 imstk_add_external_project( PThreads
-  GIT_REPOSITORY ${git_protocol}://github.com/songdongsheng/libpthread.git
+  GIT_REPOSITORY https://github.com/songdongsheng/libpthread.git
   GIT_TAG 38821d529407dcb0b4661c6805d7b1bf83f3204d
   INSTALL_COMMAND ${SKIP_STEP_COMMAND}
   RELATIVE_INCLUDE_PATH "include"

CMake/External/External_Uncrustify.cmake

@@ -3,7 +3,7 @@
 #-----------------------------------------------------------------------------
 include(imstkAddExternalProject)
 imstk_add_external_project( Uncrustify
-  GIT_REPOSITORY ${git_protocol}://github.com/uncrustify/uncrustify.git
+  GIT_REPOSITORY https://github.com/uncrustify/uncrustify.git
   GIT_TAG uncrustify-0.62
   UPDATE_COMMAND ${SKIP_STEP_COMMAND}
   CONFIGURE_COMMAND <SOURCE_DIR>/configure --prefix=<BINARY_DIR> #TODO: does not work on Windows, see --host= option
@@ -11,4 +11,4 @@ imstk_add_external_project( Uncrustify
   RELATIVE_INCLUDE_PATH ""
   DEPENDENCIES ""
   #VERBOSE
-  )
\ No newline at end of file
+  )

CMake/External/External_g3log.cmake

@@ -3,7 +3,7 @@
 #-----------------------------------------------------------------------------
 include(imstkAddExternalProject)
 imstk_add_external_project( g3log
-  GIT_REPOSITORY ${git_protocol}://github.com/KjellKod/g3log.git
+  GIT_REPOSITORY https://github.com/KjellKod/g3log.git
   GIT_TAG 6c1698c4f7db6b9e4246ead38051f9866ea3ac06
   INSTALL_COMMAND ${SKIP_STEP_COMMAND}
   RELATIVE_INCLUDE_PATH "src"