Patricia store path inferring

Environmental variable PATTY_STORE (default `.`).
Subdirectories by nativeextractor version.

Example:
```c
void get_store(patty_c *patty, const char *prefix, const char *directory);

patty_c * p = patty_create(NULL);
p->get_store(p, "v1.0.2", NULL); /* NULL for PATTY_STORE*/
```