`version` and `issue` should depend on each other

[l0b0]

With this configuration:

class { 'idea::ultimate':
  version => '14.1.3',
}

the file system ends up with this shortcut:

$ ls -l /opt/idea
lrwxrwxrwx 1 root root 20 Jun 20 18:27 /opt/idea -> /opt/idea-IU-129.451

The default build is used when a non-default version is specified. Since a version corresponds to a build we should simply get rid of the build parameter.