Co-authored-by: Srihari Dukkipati <[email protected]>

)

The variable prev_tmp_curtailment is used without initialising when
 the timepoint is not the first timepoint of the horizon and the entire
 project capacity cannot be ramped in one timepoint.

 Closes #1135

This is in prep for allowing negative power. There are small changes 
to a few objective functions, but the summary results show only minor 
differences in actual results.

* Fix transmission min targets formulation in negative direction
* Fix exporting results for transmission target contributions

* Update how hydro op chars are selected from the database to only 
select horizons on periods when the project is operational
* Update how tmp opr inputs are selected from the database to only 
select timepoints when the project is operational

Make hydro inputs handling more robust for when multiple 
balancing types may be used.

New feature to model the minimum and maximum penetration of a 
resource set at every timepoint. The requirements for this constrain 
are base and timepoint specific power limit, on general a percentage 
of the load and on ratio based on the capacity and power of other 
projects. Also created unit test for this feature.