Support for Subversion 1.7. Reading version number from .svn/entries doe...

...s not work for Subversion 1.7 because it no longer contains the version number. Also, in Subversion 1.7 there is only one top level .svn folder, and the Grails app might be located in a subfolder.

Using CLI for getting version number from 'svn info --xml' with fallback to old file based method if CLI is not installed.
This way of retrieving version number will also work for Subversion 1.6.
Handle output with a custom outputstream to prevent blocking due to a full output buffer. This was a problem on Windows.