Version change 5.2.0-SNAPSHOT to 5.2.1-SNAPSHOT for maintenence branch

Hmm - I think I might have made a mistake by rebasing my master off of the ISPN master because there are a couple of other commits from Adrian in this PR. 

If that code needs to go into this branch anyway, then I assume we don't have a problem but it's probably best if Adrian/Galder can take a look at it before merging.

I added in a line to the .gitignore so it doesn't track temporarily saved files by text editors like jedit, gedit, kwrite etc. For example, if you make a change to a pom.xml file that'll save an extra pom.xml~ file. Hence the appropriate line in .gitignore.