Introduced IrcSessionInfo
Updated examples to use IrcSessionInfo
Non-static IrcPalette
IrcPalette: revise docs and function parameter names
IrcSession: fix SSL connections

It turns out that some servers require the certificate to be requested.
QSslSocket::QueryPeer does that, but the certificate still doesn't need
to be valid. Furthermore, QSslSocket::startClientEncryption() must be
delayed until the connection is established.
desktop: gray out channel & query tree items for an inactive session
MessageFormatter: fix Irc::RPL_ENDOFNAMES handling
IrcUtil: refactor color parsing
IrcUtil: allow 1 digit (m)IRC colors
examples: a bit darker default (m)IRC colors
Introduce IrcTextFormat
Deprecate IrcUtil::messageToHtml()
examples: use IrcTextFormat
IrcTextFormat: cleanup the non-sense explicit
SessionTreeWidget: allow dragging items around

TODO: remember view order
MessageHandler: send channel notices where they belong
MessageView: expose text browser & message formatter
Desktop: remove MessagesWizardPage
MessageView: remove references to Settings::messages/highlights
Desktop: remember tree item order