Update Maven Command Line tutorial

This tutorial was originally written with a workaround in place because for a long period of time, the GA1 artifacts for Liferay 6.2 were not available from Maven Central. Now that the artifacts are available, I tweaked the tutorial to upload archetypes form Maven Central, as we've shown in the past.

I also threw in a commit correcting old links I found throughout LDN. :link: 

https://issues.liferay.com/browse/LRDOCS-1526