SPARK-1335. Also increase perm gen / code cache for scalatest when invoked via Maven build

I am observing build failures when the Maven build reaches tests in the new SQL components. (I'm on Java 7 / OSX 10.9). The failure is the usual complaint from scala, that it's out of permgen space, or that JIT out of code cache space.

I see that various build scripts increase these both for SBT. This change simply adds these settings to scalatest's arguments. Works for me and seems a bit more consistent.

(I also snuck in cures for new build warnings from new scaladoc. Felt too trivial for a new PR, although it's separate. Just something I also saw while examining the build output.)

Author: Sean Owen <sowen@cloudera.com>

Closes #253 from srowen/SPARK-1335 and squashes the following commits:

c0f2d31 [Sean Owen] Appease scalastyle with a newline at the end of the file
a02679c [Sean Owen] Fix scaladoc errors due to missing links, which are generating build warnings, from some recent doc changes. We apparently can't generate links outside the module.
b2c6a09 [Sean Owen] Add perm gen, code cache settings to scalatest, mirroring SBT settings elsewhere, which allows tests to complete in at least one environment where they are failing. (Also removed a duplicate -Xms setting elsewhere.)