Use the timeout value when finding elements

Only one of the three methods in the Browser class for finding elements was
being used and only from one call site.  Most calls to findElement were
calling selenium directly, and, as a result, not honoring the timeout value
specified in the event.

This change fixes that by creating a wrapper around selenium's findElements
in EventLoop and deleting the methods in Browser.

Testing done:

timeout-specific test.  VDD regression suite.
Add the timeout attribute to all events

This change adds the timeout attribute to all the events that don't already
have it.

Testing done:

timeout-specific test.
Add --eventtimeout command line option

The --eventtimeout command line option sets the timeout value used when
searching for elements on the page.  Setting it is equivalent to using
the timeout attribute on all events.

Testing done:

timeout-specific test script with and without --eventtimeout
Add the eventtimeout option to the config file

With this change, eventtimeout can be specified in the config file as a cmdopt.

Testing done:

timeout-specific test with all combinations of eventtimout.