Improve testing of choicn types

[chipbarnaby]

Description

1. Strengthen test cases that exercise choicn choice types (that can be given either numeric values or choices).

• The code handling these is tricky and may have been impacted during alt-string-ptr conversion.
• Test DHW_DR.cse has been added that used DHW demand response controls (using choicn inputs).
• Test 3ZAirNetAH.cse replaces 3ZoneAirNet.cse and 3ZoneAirNetCSW.cse (which were identical except for weather file). AIRHANDLER is enabled in 3ZAirNetAH.cse and it uses an expression that changes supply air temp between fixed (numeric value) and RA (return air temp control).

2. Fixed 2 bugs discovered by running regression tests with debug build.

• Incorrect conversion of Top.dateStr to CULSTR (an missing NULL in strtcat() call)
• Missing overrides for DHWSOLARSYS::Copy and DHWSOLARSYS::CopyFrom() caused incorrect handling of vector in HPWHLINK.

3. Some unused files are deleted.