Several bug fixes and small feature improvements:

    - Fix DialogCover constructor from application shutdown (#2257)
    - Fix WPushButton::setIcon() without label excess padding
    - Fix IE8 tableview 1px rendering regression
    - WCanvasPaintDevice: finishPath() after paths with alpha-color
    - Fix 2s delay without JS: (#1828)
    - Fix updating sessionID with non-standard session settings (#2191)
    - Remove stale IE(8) workaround (#2189)
    - Small bug fixes (#1816 #2173)
    - Fall back to PngImage in case of a non-JavaScript session (#1994, Bruce Toll)
    - Make TimeUtil's time invariant to date/time changes on the system
    - Fix #2213 Wt::WTableView->selectionChanged() signal not sending upon non-standard deselection