improve webapp parameter checks

<xnox> popey: dholbach: why are the reviews manual, and not automatic? plus those error messages appear to be generated.
<dholbach> xnox, automatic reviews are in the works
<xnox> popey: dholbach: also neither of those options are available in saucy, are they? so webapps that use those command line options are broken on saucy / stable.
<dholbach> xnox, I have no idea about that
<xnox> popey: dholbach: so i should be bumping the spec/dependencies on the webapps/webrowser framework.
 popey: dholbach: or saucy should get an SRU to not error out on those options (make them dummy)
<xnox> popey: dholbach: the result of the check is wrong, i'm using old-style "webbrowser-app" exec line, not the new style "webapp-container"
<xnox> popey: dholbach: the old one allows running the apps just fine (and actually executes webapp-container underneath)
<dholbach> xnox, aha!
<xnox> popey: dholbach: since my apps actually do work on trusty, please accept them as is and improve the automatic checks about parameters to be applied against webapp-container.

"error": { "desktop_Exec_webbrowser_required (lloyds-bank-uk)": { "text": "must specify one of --webappUrlPatterns or --webappModelSearchPath" }