Small CASTEP and GROMACS benchmarks for UCL resources

[owainkenwayucl]

CASTEP al3x3:

• Myriad (Tier 3 HTC service, Skylake)
• Grace (Tier 3 HPC service, Haswell)
• Thomas (Tier 2 HPC service, Broadwell)
• Michael (Tier 2 HPC service, Broadwell)

GROMACS 1400k:

• Myriad
• Grace
• Thomas
• Michael

GROMACS large:

• Myriad
• Grace
• Thomas

[aturner-epcc]

Thanks @owainkenwayucl. Sorry for the delay in merging these!