In the last installation of STS I made, when I had the support of SVN by installing Subversive (from Menu > Help > Install New Software), Eclipse (Kepler) didn't ask me for the SVN connector I wanted to use. In this kind of situation, I discovered that it's possible to install it from an update site provided by Polarion.
So, go to to Polarion, and check out the url from the Download section. Here is the one I used :
Then you can install your SVN connector (for me, it's always SVNKit which is a pure Java implementation connector).