robustness updates

• The handling of missing/invalid mex file was incorrect.
• If a column name in the SQLite database is an invalid field name in Matlab, the mex implementation would create the struct with an invalid field name. A sanitization is now implemented to convert the column names (similar to how jsondecode works).
• A NULL value is now returned as NaN, instead of causing an error. BLOBs will still cause an error.

complete redesign

C interface changed so compile from source should be possible without extensive knowledge of C++ internals
Name,Value syntax added (as struct)
added functionSignatures.json
CLI removed
exception redirection added
subfunction updates

move from FEX to GitHub

Updates include a reworked method to retrieve binaries and (for Octave) to compile them on the fly from source.