Add activation, item_updater and version

Implement part of functions of Activation, ItemUpdater and Version.

Tested: Upload a dummy PSU tarball, and verify the activation object is
        created with expected ExtendedVersion, and the object is deleted
        when Delete is invoked.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I7b9d29f46914ace93d27a715b32c80957e88a0aa
diff --git a/meson.build b/meson.build
index 0e8a289..bc5e1b8 100644
--- a/meson.build
+++ b/meson.build
@@ -3,7 +3,8 @@
         default_options: [
           'warning_level=3',
           'werror=true',
-          'cpp_std=c++17'
+          'cpp_std=c++17',
+          'b_lto=true',
         ])
 
 systemd = dependency('systemd')