Prefer LD_LIBRARY_PATH to hardcoded search paths

[PierceNg]

For server-side and also packaged desktop applications, it is preferable to load a known specific libsqlite3.so that has the necessary features compiled in, to using whatever libsqlite3.so the OS happens to supply.

BTW, on Ubuntu 18.04 the system-supplied libsqlite3.so lives in /usr/lib/x86_64-linux-gnu which isn't in the current hardcoded paths.