Make cmake find freerdp v1.2
Make cmake find libssh v6
Migrate nx plugin to GTK3 and libssh 0.6. Fixes #365.
Migrate VNC plugin to GTK3. Fixes #365.
Different cert names for different ports. Fixes #373

Fixes certificate handling when connecting to the same host but on different ports, directly or via ssh.
Migrate remmina_applet_menu_item to GTK3. Fixes #365.
Migrate remmina_connection_window.c to GTK3. Fixes #365.
Fix pointer used after free
Merge pull request #393 from giox069/next

Varoius fixes