IPPL/FFT cleanup:
- header added to file
- obsolete files removed
- line indentation fixed
- required functions and macros moved from c_utils.{c,h} moved to fftpack.cpp

replace integer argument to operator[] with Index argument; Test file in issue #229 runs to the end and also all regression tests yield correct results

adding RN source which behaves like a singleton if no seed is provided for a single SAMPLING; A seed for the singleton instance can also be provided. Allow randomly generated sample in the 'sequence sampler'; Now the difference between the sequence sampler and the sampler is that the latter samples a sub-space of the N-dimensional space (where N is the number of DVars). The dimension of the sub-space can vary between 1 and N (no randomly generated sequences and all sequences randomly generated respectively). @frey_m We should consider to rename the SEQUENCE attribute.

Further changes:
   - remove SIMTMPDIR attribute

modified:   src/OpalConfigure/Configure.cpp
modified:   src/Sample/CMakeLists.txt
modified:   src/Sample/OpalSample.cpp
modified:   src/Sample/OpalSample.h
modified:   src/Sample/SampleCmd.cpp

deleted:    src/Sample/SequenceSampleCmd.cpp
deleted:    src/Sample/SequenceSampleCmd.h

Sample

Add new feature of optimiser: Sampling mode.

Closes #225

See merge request !38