Wiki Support as in-sdk help

Currently, our wiki is on a somewhat 3.0 state and we cannot update it further without reworks.
How it worked so far was:

1. There is jme3-documentation/src/com/jme3/gde/docs/wiki-download-index.properties containing "all available wiki pages",
2. In jme3-documentation/src/com/jme3/gde/docs/build.xml, a feature of the old wikl is used:

<get src="${wiki_url}${page_name}?do=export_xhtmlbody"
             dest="src/${javahelp_path}/${page_path}.html"/>

3. There are some post processing ant tasks which fix up the html exports (e.g. changing http links to internal links, downloading images).

Now there are two ways for the new wiki:
A) Don't use any export and pull in the whole html. This works good because the new wiki is very lean with regards to the code. There are, however, dependencies to font awesome and some other css files. Those would have to be relocated and delivered for it to work locally.

B) Use the existing asciidoc files and generate fresh sdk-ready html files. This would be a way cleaner way of doing things, but won't work if we decide to switch the wiki again. BUT we would have more control over the process. This however means spending a weekend to learn ascidoc.

Edit: Problem #1: The search uses https://cdn.jsdelivr.net/docsearch.js/2/docsearch.min.js with an API Key, so that won't work offline already.

Read jme3-documentation/src/com/jme3/gde/docs/wiki-download-index.properties and build.xml to understand the current export and post-processing flow. Compare the proposed whole-HTML and generated-HTML approaches, including the offline search dependency noted in the edit. Done should provide wiki help in the SDK without relying on unavailable external resources.