Add demand flexible CDL sequences to the buildings librayr

[anandkp92]

As part of the CEC funded OBC-Flex project, we will be developing rule-based demand flexible CDL sequences. These sequences should be part of the buildings library and I'm creating this issue to track this development.

The CDL sequences will

1. implement specifications from LBNL's Fault-Free Optimal Control Project project and the OBC-Flex project
2. include semantic constraints/shapes as part of the sequence (through semantic annotations)
3. include validation tests with applicable system models