* disable builds of the StructChecker code by default
* operator"" _smarts() doesn't need to catch sanitization errors
* remove unused function
* turn back on some tests that shouldn't have been disabled
* Remove unused code from SMARTS parser and simplify a bit
SmilesParseOps::AddFragToMol is now used only from the SMARTS parser, so we can simplify the API
* Removes obsolete special case code for SMARTS
This was relevant when organic atoms in SMARTS queries were stored as two-part queries.
* improve SMARTS testing
make sure we can generate SMARTS from all the examples and then parse that again.
* Fixes#2814
* Fixes#2815
* some additional smarts tests to improve coverage
* test copy ctor and getPos
* remove obsolete test_list files
* include tests for the morgan invariant generators
* more cleanups and coverage improvements
* remove files that were mistakenly added
