Update src/shared (NOTE: git submodule update)

Includes tweaked MessageFormatter to get a smaller timestamp and
working nick colors...
Add preliminary handling for reserved nick name & wrong channel key
Say hello to side panels

The list of buffers (on the left) and users (on the right, when
on a channel) have been moved side panels that can be opened by
swiping side ways. This makes it convenient to quickly peek the
list of buffers whether there are any new/highlighted messages,
whilst the real screen estate is still reserved to the textual
content.
Nick colors based on Theme.highlightColor (NOTE: git submodule update)
Remove remaining "communi" references from the GUI

- change the default nick & username to SailorXXXX/sailfish
- remove #communi from the list of default channels

Communi is no longer visible in the GUI - it's now merely
a project/working name.
Implement #3: "Remorse" removal for connection items
Add BufferProxyModel::get(index)
Avoid sending empty JOIN commands
BufferListPanel: visualize active highlights
MessageModel: clear active highlight when activated (entering a page)
BufferPage: handle Qt.application.active
TextEntry: disable the enter key when there's nothing to send
Revise connection/buffer removal

Replace the current buffer with prev/next & open the connect dialog
when the last connection is removed.
Restore 08239ad184bb7fb5e1dc0d45e2b433a68ef2c70c

The change went missing during the side panels refactor
Open NickDialog when nick is reserved
PanelView: hide when appropriate instead of just making non-interactive

This ensures that those side highlight bars won't be visible when
there's for example a dialog open on top
Make BufferDelegate less prone for warnings
MessageModel: add support for plain text (NOTE: git submodule update)
Add context menu item to copy messages
Don't allow swiping the side panels over the textfield

Ref: #15 - Improve side panels