Multiple Contrasts

- Added support for multiple contrasts
- Added basic framework for multiple factors
- Added additional information to html output
- Added function for producing html images
- Changed image output format from pdf to png
- Changed input for plotMDS from .rda to .csv
- Removed option for robust estimation of dispersion, now on by default

- Need to reformulate sampleanno assignment
- Need to fully support multiple factors without contrast options
- Need to produce pdf outputs to accompany png