Added installation config to meson

meson.build

@@ -1,3 +1,6 @@
 project('camera', 'c')
 gtkdep = dependency('gtk+-3.0')
-executable('camera', 'main.c', 'ini.c', dependencies : gtkdep)
+executable('camera', 'main.c', 'ini.c', dependencies : gtkdep, install : true)
+
+install_data(['camera.glade', 'camera.css'],
+             install_dir : get_option('datadir') / 'camera/ui')