add optional export support to Web.pm

	modified:   modules/Accessory/lib/CoGe/Accessory/Web.pm
add support to set default config options

Options can be changed in the config by passing a hash of options to
set_defaults.

	modified:   lib/CoGe/Accessory/Web.pm
add url building support

Add new function url_for to construct URL.

	modified:   modules/Accessory/lib/CoGe/Accessory/Web.pm
	new file:   modules/Accessory/t/url.t
refactor get_dotplot

Refactor get_dotplot to fix URL construction and fix bug with URL
not being constructed properly.

	modified:   web/SynMap.pl
improve dotplot URL building

Refactor dotplot.pl to construct URL using url_for. fixes an issues
where the URL is not constructed correctly when the config doesn't have
a base url.

	modified:   web/bin/dotplot.pl
	modified:   web/tmpl/widgets/Dotplot.tmpl