Add i18n basic structure

Closes #3.

po/POTFILES.in

@@ -0,0 +1,25 @@
+src/calls-call-data.c
+src/calls-call-display.c
+src/calls-call-holder.c
+src/calls-call-selector-item.c
+src/calls-dummy-call.c
+src/calls-dummy-origin.c
+src/calls-encryption-indicator.c
+src/calls-main-window.c
+src/calls-mm-call.c
+src/calls-mm-origin.c
+src/calls-mm-provider.c
+src/calls-new-call-box.c
+src/calls-ofono-call.c
+src/calls-ofono-object.c
+src/calls-ofono-origin.c
+src/calls-ofono-provider.c
+src/calls-party.c
+src/ui/call-display.ui
+src/ui/call-selector-item.ui
+src/ui/call-window.ui
+src/ui/encryption-indicator.ui
+src/ui/history-header-bar.ui
+src/ui/main-window.ui
+src/ui/new-call-box.ui
+src/ui/new-call-header-bar.ui