Ccorrectly copy default startup files when necessary
* We're careful not to overwrite existing startup files in "content/thredds"
* Corrected the production release value of "tds.content.root.path" in tds.properties.
* Added a step in release.txt to ensure that production values are used when making a release.
Merge branch '4.5.4' of https://github.com/Unidata/thredds into 4.5.4