[geary] Chase Meson build to use XDG Help spec locations.

[Michael Gratton <mjog src gnome org>]

commit 37c218d646dc9976e761e44fe31d767b93bef4ac
Author: Michael James Gratton <mike vee net>
Date:   Mon Jan 15 14:11:24 2018 +1100

    Chase Meson build to use XDG Help spec locations.
    
    * src/client/application/geary-application.vala (Application): Use "help"
      and yelp for showing help, rather than old "ghelp" URI and gnome-help.
    
    * help/CMakeLists.txt: Update CMake build to match Meson

 help/CMakeLists.txt                           |    8 ++++----
 src/client/application/geary-application.vala |    4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/help/CMakeLists.txt b/help/CMakeLists.txt
index 24b454f..3f9715c 100644
--- a/help/CMakeLists.txt
+++ b/help/CMakeLists.txt
@@ -26,15 +26,15 @@ set(TRANSLATED
     sv
 )
 
-set(HELP_DEST share/gnome/help/geary)
+set(HELP_DEST share/help)
 
 set(HELP_SOURCE)
 foreach(_page ${HELP_FILES})
     set(HELP_SOURCE ${HELP_SOURCE} C/${_page})
 endforeach()
 
-install(FILES ${HELP_SOURCE} DESTINATION ${HELP_DEST}/C)
-install(FILES C/figures/geary.svg DESTINATION ${HELP_DEST}/C/figures)
+install(FILES ${HELP_SOURCE} DESTINATION ${HELP_DEST}/C/geary)
+install(FILES C/figures/geary.svg DESTINATION ${HELP_DEST}/C/geary/figures)
 
 # Hacked together from the similar macro in cmake/Gettext.cmake.
 MACRO(HELP_CREATE_TRANSLATIONS _firstLang)
@@ -66,7 +66,7 @@ MACRO(HELP_CREATE_TRANSLATIONS _firstLang)
                     WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
                     )
 
-                INSTALL(FILES ${_destPage} DESTINATION ${HELP_DEST}/${_lang})
+                INSTALL(FILES ${_destPage} DESTINATION ${HELP_DEST}/${_lang}/geary)
                 SET(_translatedPages ${_translatedPages} ${_destPage})
             ENDFOREACH()
         ENDIF()
diff --git a/src/client/application/geary-application.vala b/src/client/application/geary-application.vala
index 65481f3..00625c2 100644
--- a/src/client/application/geary-application.vala
+++ b/src/client/application/geary-application.vala
@@ -462,12 +462,12 @@ public class GearyApplication : Gtk.Application {
     private void on_activate_help() {
         try {
             if (is_installed()) {
-                show_uri("ghelp:geary");
+                show_uri("help:geary");
             } else {
                 Pid pid;
                 File exec_dir = get_exec_dir();
                 string[] argv = new string[3];
-                argv[0] = "gnome-help";
+                argv[0] = "yelp";
                 argv[1] = GearyApplication.SOURCE_ROOT_DIR + "/help/C/";
                 argv[2] = null;
                 if (!Process.spawn_async(