For E2E rooms, display "Send an encrypted message…" otherwise display "Send a plaintext message…" as the placeholder for the input box in [old] message composer.
This adds a 5 minute auth cache to speed up the process of deleting
old devices. It has the following nastinesses (mainly due to being
written on a flight whilst juggling kids):
* the auth cache is done as context attached to MatrixChat.
one could argue that it should be per-client instead, but we don't
yet have multiple clients.
* the auth cache is only maintained currently in DevicesPanelEntry
(i.e. set & invalidated). One could argue that it might be better
maintained in InteractiveAuth.js or a dedicated cache object
abstraction, but given the only use I can think of is when managing
devices, perhaps this is good enough for now.
To fix https://github.com/vector-im/riot-web/issues/2916, force the checking of scroll position by calling _onWidgetLoad (might need renaming...) when a MELS is expanded/contracted.
Also use an keying scheme for MELS that doesn't depend on the events contained, but rather a simple incrementing index based on the order of the MELS as it appears amongst all MELS.
Revert the WithMatrixClient change: RoomView calls methods on
the RoomSettings component and this breaks when RoomSettings is
wrapped in a WithMatrixClient.
Into a component that does Interactive Auth and a dialog that
wraps it, so we can do interactive auth not necessarily in a
dialog.
As a side effect:
* Put the buttons for each auth stage in the stage itself.
Some stages don't have submit buttons (and it's very possible
other stages may have other buttons entirely, like 'resend')
so it makes more sense for the buttons to live in the stage
components themselves. Plus it saves the slightly evil
calling-functions-on-react-children thing we were doing (and
indeed extending that to show the submit button at all).
* Give all BaseDialogs a cross in the top right to cancel. They
were all dismissable by clicking outside or pressing esc, so
this adds a more visually obvious way of dismissing them. Plus,
it means our InteractiveAuthDialog can have a way of canceling
the whole operation separate from buttons for the individual
stages.
