Revamp IrcXxxModel sorting once again

Add sortOrder as a property, and replace dynamicSort
with an additional sort method - Irc::SortByHand.
Fix up the model sorting docs
Update CHANGELOG [skip ci]
examples/bot: add support for -user & -password cmd line args
Exclude qmlbot & quick examples when the Qt modules are not avail
Exclude the QML plugin as well if QtQml is not available
Restore IrcPalette as a grouped property for IrcTextFormat
IrcPalette: set expected default values no matter how ugly they are

It makes no sense to provide random default values that might look
better in some very specific context eg. in a GUI client on top of a
light background. Instead, match the default values to the property
names.
Fix Qt4 build
Turn invokable IrcConnection::sendXxx() to slots
Declare the rest IrcUtil meta types
Scale down the example screenshots
Properly handled all known percent encoding cases and exclusions using QURL::toPercentEncoding().
tst_IrcTextFormat: add a couple of urls to test
Bump the version - master continues as 3.0.1
IrcConnection::open(): bail out when the connection is already active

This way the open() slot can be safely connected to multiple signals,
and QAbstractSocket won't throw the "already connecting" warnings...
IrcPalette: add missing export macro
IrcTextFormat::toHtml(): exclude percent encoding for hash marks
IrcTextFormat::toHtml(): exclude percent encoding for = and ?
IrcTextFormat::toHtml(): exclude percent encoding for + and &