functions to test different ranks and algorithms,extract results info

[ccpalu]

These are functions to optimize the use of nmf package

• nmfExplore: makes it easier to run the analysis with all available nmf algorithms, for a range of rank values. They are plotted along the same analysis for random data. The results are saved in a folder and the user can examine them to support the decision on the rank factor and algorithm to use.
• runNMF: after the user chooses the algorithm and rank, this function will do the nmf analysis but will also extract information on the metagenes, main features contributing to the definition of metagenes, W, H, to which metagene each column/row was assigned more frequently. All will be saved in files.

In both cases, we also save some environment variables in case the user wants to do further analysis and exploration with the results.