Improve user guide: be more consistent

### Change Overview

In the user guide,

- [x] favor `Javadoc` over `javadoc`, consistently.
- [x] favor `Groovy` over `groovy`, consistently.
- [x] favor `Ant` over `ant`, consistently. 
- [x] favor `Java` over `java`, consistently.

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- I did not attempt to fix `jar` vs `JAR`. There were roughly 76 instances of `jar`, 43 of `JAR` (including literals, paths, etc).
- Similarly, I did not attempt to fix `war` vs `WAR`.

I may have missed some, but this makes the user guide more consistent and (hopefully) easier to read.