Use the QAction provided by QDockWidget with new Qt connection rather
than creating a new one for each dock.
Separate extra browser docks from extra docks, the latter is meant for
plugin/integration docks.
The removeIconSmall is now also a trash icon, so we don't need a
separate (now duplicate) themeID for it anymore.
The icon itself of course needs to stay as it's still needed.
The extra browser panels would always create on startup due to the
visibility change. This fixes that by ensuring that this call blocks
signals, and ensures that the call only happens on first creation by the
user and not when the user is loading on startup.
In the view -> Docks menu, when a user first creates a custom browser
dock, the menu item associated with them used to hide/show them will be
unchecked in the menu by mistake. This ensures they're checked when
first created.
Allows the ability for users to add custom browser widget docks that
they can use for their third party services if they feel the need,
mostly as a convenience tool so they don't have to open extra browsers
alongside the program.
