v0.7.5-alpha — drag to reorder tabs, reconnect uses the edited credentials

New

Tabs can be reordered by dragging. Drag a tab along the bar; a marker shows where it
will land, the tab follows the pointer, and the order is kept across restarts.

Worth a note on how, because the obvious approach does not work here: this is a plain drag
gesture with the tab positions hit-tested by hand, not the system drag-and-drop API. That
API brought a snapshot image drawn over the bar, drop targets that competed with each other
and silently swallowed drops, and no callback when a drag is abandoned. mRemoteNG has the
same constraint on Windows and resolves it the same way — DockPanelSuite never calls
DoDragDrop, it captures the mouse and tracks the moves itself.

The selected tab is scrolled into view. Opening a connection from the sidebar selects
its tab, but with enough tabs open that tab could be off-screen — selected and invisible
until you scrolled the bar by hand.

Fixed

Reconnect used the password from when the tab was opened. Connecting with wrong
credentials leaves the tab on a logon failure; editing the password and hitting Reconnect
retried with the old one, and the only way to pick up the change was closing the tab and
opening the connection again from the sidebar. The credentials are now re-read from the
connection on every reconnect. "Copy password" had the same problem.