A bad regex pattern was being used to remove files ending with ".gdx".

Allow providing additional SLURM parameters via cfg$slurmConfig. Parameters that are later provided interactively via start.R overwrite the cfg values. Closing #139

* Enable prepare_and_run.R to restart fixed runs (https://github.com/remindmodel/remind/issues/112)
* Enable start.R to restart non-optimal runs

Reintroduce bound on biomass relative to reference scenario to prevent regions with large carbon storage potential from deploying BECCS in tight policy cases only to produce negative emissions rather then generating energy.

- makes it executable from the command line without invoking Rscript
  explicitly
- saves on typing, makes for more relaxed REMIND work ;)

- testOneRegi runs are useful for fast development iterations ("do these
  changes break the model, or does it still run"), so setting them up
  should be fast as well

- supplying the parameter "--testOneRegi" to start.R will ignore any
  scenario_config file provided and modify the default configuration to
  start a testOneRegi run in the directory output/testOneRegi with no
  output processing
- the old oneRegi.R script and oneRegi.cfg configuration are deleted

- existing output/testOneRegi directories are overwritten

Refactoring start scripts: - delete start_functions.R because all it's functions have been replaced by new ones
- fix bugs and correct formatting in other files

Refactoring start scripts: - moved the definition of the slurm strings from  submit() in submit.R to choose_submit() in start.R
- renamed the function choose_submit() to choose_slurmConfig() and moved it to the new file choose_slurmConfig.R

Refactoring: -start scripts (part 5): renamed submit_run(cfg) into submit.R(cfg), deleted conopt files

Refactoring: - part 2: restructure start scripts (try to minimize workload for the login node on the cluster when starting a REMIND run by moving code into scripts that are included in the slurm job)

Refactoring: - restructure start scripts (try to minimize workload for the login node on the cluster when starting a REMIND run by moving code into scripts that are included in the slurm job)