GROMACS tweaks

* move to GROMACS v4.6.1
* include downloading and running of GROMACS regtests
* use `goolfc` toolchain for CUDA-enabled build

Unit tests pass beautifully for both type of builds:

```
== 2013-04-24 06:19:39,329 main.filetools INFO cmd "make check" exited with exitcode 0 and output:
-- Configuring done
-- Generating done
-- Build files have been written to: /home-2/khoste/.local/easybuild/build/GROMACS/4.6.1/goolfc-1.3.12/gromacs-4.6.1
Linking CXX static library libgpu_utils.a
[  0%] Built target gpu_utils
Linking CXX static library libcuda_tools.a
[  0%] Built target cuda_tools
Linking CXX shared library libgmx.so
[ 62%] Built target gmx
Linking CXX static library libnbnxn_cuda.a
[ 62%] Built target nbnxn_cuda
Linking CXX shared library libmd.so
[ 74%] Built target md
Linking CXX shared library libgmxana.so
[ 89%] Built target gmxana
Linking CXX executable editconf
[ 89%] Built target editconf
Linking CXX shared library libgmxpreprocess.so
[ 94%] Built target gmxpreprocess
Linking CXX executable grompp
[ 96%] Built target grompp
Linking CXX executable pdb2gmx
[ 97%] Built target pdb2gmx
Linking CXX executable gmxcheck
[ 98%] Built target gmxcheck
Linking CXX executable mdrun
[100%] Built target mdrun
Scanning dependencies of target gmxtests
[100%] Built target gmxtests
Scanning dependencies of target check
Test project /home-2/khoste/.local/easybuild/build/GROMACS/4.6.1/goolfc-1.3.12/gromacs-4.6.1
    Start 1: regressiontests/simple
1/5 Test #1: regressiontests/simple ...........   Passed    9.05 sec
    Start 2: regressiontests/complex
2/5 Test #2: regressiontests/complex ..........   Passed   10.77 sec
    Start 3: regressiontests/kernel
3/5 Test #3: regressiontests/kernel ...........   Passed   75.34 sec
    Start 4: regressiontests/freeenergy
4/5 Test #4: regressiontests/freeenergy .......   Passed    8.57 sec
    Start 5: regressiontests/pdb2gmx
5/5 Test #5: regressiontests/pdb2gmx ..........   Passed   28.58 sec

100% tests passed, 0 tests failed out of 5

Total Test time (real) = 132.91 sec
[100%] Built target check
```