fix wrong file paths in uninstall
adds an upsell message to the footer of the main plugin page
Merge pull request #368 from humanmade/fixes-uninstall-file-refs

fix wrong file paths in uninstall
rename add-on to extension
Merge pull request #369 from humanmade/upsell-pro-addons-369

add upsell sentence for Pro addons
schedule sentence escaping
correct some language
Merge pull request #370 from humanmade/correct-language

correct some language
Merge branch 'master' into enable-intercom-support-366

Conflicts:
	admin/page.php