Added first version of demand response client.
Added Sources package to Buildings.Controls

This is need for the demand response models, and is also useful for
other applications.
Revised demand response models.
Added array to baseline model
Added array to baseline model
Improved documentation.
Revised model.

Corrected bug in baseline computation.
Updated documentation.
Added test case for building 90 data.
Separated baseline computation into its own block.
Renamed BaselineComputation
Renamed model
Added weather regression model.

Added weather regression model.
Made various small improvements.
Revised documentation.
Changed normalization of error.
Set T to a zero-sized vector.

This significantly reduces the size of the compiled code for the parameter setting that does not require T.
Added initialization for all states to avoid a warning.
Merge branch 'master' into demandResponse
Added sampler to input.
Removed the pre() operator which is not allowed in an algorithm section.
Changed input from power to energy to separate the integration from the implementation.