"# don't import net directly, import the module instead (so that net is singleton)"
set_as_network does not work if net is not a singleton, it results in a split worldview.
don't return the spending methods pay_invoice and multi_pay_invoice in
the get_info request and the info event so connections can be used for
services that enforce receive only connections.
store all plugin data by plugin name in a root dictionary `plugin_data`
inside the wallet db so that plugin data can get deleted again.
Prunes the data of plugins from the wallet db on wallet stop if the
plugin is not installed anymore.
