Use dot for type seperation
Split HistoryPicker for use it without a PopupPlugin

To be able to use the HistoryPicker core logic in other contexts,
we split off the history management logic into a HistoryController
class that supports, and is in fact based on the standard Plugin
interface. This allows for histories to be created at runtime from
within another plugin. There is currently no way to connect this
history and its signals to the outside world without connecting
the events manually in the instantiating plugin.

Additionally the PopupPlugin.popup method now accepts an items
parameter that, when provided, will be used instead of the items
method on the plugin. This allows for multiple popups from the same
plugin with different content without handcoding the logic of the
popup method.
Add a ClipboardExchange plugin to share your Clipboard

The plugin lets you configure shared hmac and aes secrets
to encrypt all traffic, as well as a list of users via
"user.<name> = ip[:port]". You can then suggest the contents
of your clipboard to one of those users via a popup menu.
The other user will then get a notification and can accept
the suggestion as his current clipboard contents.

Suggestions may be reviewed later on with another popup
menu that shows all suggestions on a per user basis.

The relevant options and defaults are configure in the
exmaple config file.