Fix return value of Builder.usingServer to a self-reference

It is documented as returning a self-reference (and this is useful
for chaining), but before this commit was instead returning
the string passed to it.

Signed-off-by: Andreas Tolfsen <ato@mozilla.com>
Eclipse classpath fixes for htmlunit.

Signed-off-by: Simon Stewart <simon.m.stewart@gmail.com>
HtmlUnitDriver: Initial code cleanup.

Notably: imports have been reorganized, missing @Overrides added and
calls to depreacted APIs have been removed.

Signed-off-by: Simon Stewart <simon.m.stewart@gmail.com>