Merge pull request #55 from infirit/master

Add  to ACLOCAL_AMFLAGS for user added flags
configure: Bump minimum versions
libview: Add GTK3 support
shell: Add GTK3 support
Bump version to 1.7.0
Sync translations with transifex
previewer: Fix g_thread_init deprecation
libview: gdk_display_get_app_launch_context is available only in GTK3

Add fix for GTK2
Update copyright in about dialog
Remove unneeded gdconfig.h include
Use GTK_API_VERSION for g-ir-scanner instead of hardcoded version