LPS-34521 The default (help) template displayed for web content is not the one meant for DDL
LPS-34520 Remove the ability to provide different help message per Application Display Template type

This is not so useful now that we have the palette and it' s just adding noise (and more maintenance work). I have decided to leave it in the framework so that third party developers still have the freedom to provide their own custom help messages for their template types.
LPS-34520 Improve default (help) content when creating a new template

The texts were proposed by Product Management. I've made sure that we don't use more than 70 lines since it's the size of some of the text areas we use for templates.
LPS-34520 Fix grammar and inconsistencies in text produced by Product Management, for example:

1.) "an specific application" is not correct, it should be "a specific application".

2.) If we reference it in one place as "Web content templates", then "Web Content Structure" being a title is inconsistent. In Language.properties activity-*, we reference things as "web content xyz". So within the same sentence, "Web content templates" is used as a phrase, where as "Web Content Structure" is used as a title. I'm making them the same and using phrases to match Language.properties activity-*.

3.) I struggled with whether we should go with: typing $ / typing ${ or with typing "$". and typing "${". While the latter may be confusing because it has an additional " and an ending period, it's techincally correct grammar to make a sentence. For those who are used to seeing a correct sentence, their minds should auto adjust and know that we're talking about the stuff inside the quotes, and that it doesn't include the quotes. Otherwise, they'll just thin that the sentence as never finished. Either way, someone can be confused, so I'm opting for confusing the person who is not expecting the sentence to finish vs. the one who naturally expects a complete sentence.