Minimize WildFly-specific stuff in welcome-content

There are a number of welcome-content things that result in the need for overly complicated changes to convert the welcome-content for other branches (e.g. EAP).

1) Get rid of copyright headers.
2) Use HTML 5 DOCTYPE tag instead of 4.
3) Rename files like wildfly.css to something generic so the same file name can be used elsewhere, just with different content. (This is probably a bad idea as looking at the css the files are so different that they aren't really different variations of the same thing. Using the same file name will just lead to spurious merge conflicts.)
4) Add this:

    <!-- proper charset -->
    <meta http-equiv="content-type" content="text/html;charset=utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE8" />

5) Clean up various whitespace etc stuff.