When copying options when they exist

* When copying options from one Options object to another,
  don't copy an option if it is empty (thereby deleting it)
Variable is now a Component

* Variables take options
* Variables are defined in schemes.nl
* Runs and configurations can choose to load certain derived variables
* Temporarily disable many derived variables (Power, etc)
Added new variables
Added appendOption to Options
Append variables from run and configuration

* When creating a data object, variables from both the run and
  configuration should be used
Define auxiliary downscaler in run
Allow each variable to have its own downscaler

* Variables and their downscalers are defined in runs using
  'downscalerVariables' and 'downscalers'
Safer handling of derived variables
New namelists
Added elevation downscaler for pressure

* More accurate computation of min, mean, max in Info driver
* More accurate calculation of wetbulb temperature

Conflicts:

	src/Drivers/Info.cpp
Allow InputFlat to write to file
New variables
Allow Threshold metrics to be on an interval

Conflicts:

	graphics/files/VerifPlot.py
Bug fix in ContinuousBpe

* BPE does not need parameter estimation. Therefore an external
  estimator should not be used.
* Previously using this scheme caused an abort on initialization.
Check for missing values when using overflow probabilities
Bug in updating pooled parameters

* When multiple observations were used to update parameters, incorrect
  weighting caused the parameters to be scaled by the number of
  observations, instead of being given a greater weight.
* For now the weighting has been disabled, since it is not clear if it
  makes sense to weight by number of observations.
Improvements to convert.exe

* Allow subset of variables to be created
* Create the new namelists
* Specify downscalers for each variable
Add extended logistic regression

* Added ContinuousElr
* Allow Continuous schemes to use Estimator to estimate parameters
  externally
Minor bug in options when whitespace at the end

* If an options line ends in white space, "=1" gets added to the
  options. Shouldn't affect anything.
Check unused keys in options

* A typos in the attribute name in a namelists would lead to the key
  being ignored, without any warning. Now each scheme checks that all
  attributes have been read, and provides a warning if not.

Conflicts:

	src/Inputs/Dvh.cpp