Add -Wall -Wextra -Werror compilation flags

[d-serj]

This PR enables GCC/Clang compiler warnings (-Wall -Wextra -Werror) for both library and unit tests, and adds optional AddressSanitizer support. All warnings found by the new flags are fixed.

Bugs fixed while enabling warnings:

• websocket.c - return value of lws_write() was incorrectly compared against an unsigned variable so that negative error codes were not detected
• eebus_data_choice.c - IsNull() and IsEmpty() were returning an error code integer through bool return type

Warning fixes:

• Added UNUSED() macro calls for unused function parameters
• Fixed struct initializer syntax ({0} -> {{0}}) in test files and spine model enum tables (-Wmissing-field-initializers)
• Fixed printf format specifiers in EebusDateToString() to use %u matching the unsigned cast (-Wformat)
• Reordered null checks in StringLutRecordInit() and Uint64LutRecordInit() so memset is never reached with NULL pointer (-Werror=maybe-uninitialized)

[gennadiyvt]

Added some nice-to-have remarks

[mansandersson]

Thank you for your contribution