Linux - Replace legacy desktop integration with modern XDG-based integration

Replace manual placement of .desktop files with modern XDG-based install process.

Update .desktop file to leverage modern XDG functions (namely, the ability for an application to request to be ran on the system's most powerful GPU, useful for hybrid graphics setups).

Also provides provisions for launching the viewer on the iGPU and associating SLURLs via the desktop file, accessible by right-clicking the desktop shortcut.

indra/newview/linux_tools/install.sh

@@ -55,11 +55,13 @@ function homedir_install()
 
     prompt "Proceed with the installation? [Y/N]: "
     if [[ $? == 0 ]]; then
-	exit 0
+	    exit 0
+    fi
+    if [[ -d "$XDG_DATA_HOME" ]] ; then
+        install_to_prefix "$XDG_DATA_HOME/alchemy-install" #$XDG_DATA_HOME is a synonym for $HOME/.local/share/ unless the user has specified otherwise (unlikely).
+    else
+        install_to_prefix "$HOME/.local/share/alchemy-install" #XDG_DATA_HOME not set, so use default path as defined by XDG spec.
     fi
-
-    install_to_prefix "$HOME/.local/share/alchemy-install"
-    $HOME/.local/share/alchemy-install/etc/refresh_desktop_app_entry.sh
 }
 
 function root_install()
@@ -77,7 +79,6 @@ function root_install()
     install_to_prefix "$install_prefix"
 
     mkdir -p /usr/local/share/applications
-    ${install_prefix}/etc/refresh_desktop_app_entry.sh
 }
 
 function install_to_prefix()
@@ -124,6 +125,8 @@ function install_to_prefix()
         rm "$1/bin/llplugin/.user_does_not_want_chrome_sandboxing_and_accepts_the_risks" 2> /dev/null
         pkexec "$1/etc/chrome_sandboxing_permissions_setup.sh" || die "Failed to set permissions on chrome-sandbox"
     fi
+    sh "$1/etc/refresh_desktop_app_entry.sh" || echo "Failed to integrate into DE via XDG."
+    set_slurl_handler "$1"
 }
 
 function backup_previous_installation()
@@ -134,6 +137,16 @@ function backup_previous_installation()
     mv "$1" "$backup_dir" || die "Failed to create backup of existing installation!"
 }
 
+function set_slurl_handler()
+{
+    local install_dir=$1
+    prompt "Would you like to set Alchemy as your default SLurl handler? [Y/N]: "
+    if [[ $? == 0 ]]; then
+	exit 0
+    fi
+    "$install_dir"/etc/register_secondlifeprotocol.sh #Successful association comes with a notification to the user.
+}
+
 
 if [ "$UID" == "0" ]; then
     root_install