chore: remove unused hashtable and dead code

Remove hashtable module and tests (unused in runtime). Remove unused
variables mycolour, direction, output_scale_factor, and dead local p.

tests/test_hashtable.c

@@ -1,63 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-#include <stdio.h>
-
-#include <hashtable.h>
-
-void test_hashtable(int size) {
-	hashtable h =  hashtable_new(size);
-	void *value1 = "to jest jakaś tam wartość";
-	void *value2 = "I inna";
-	void *value3 = "trzecia";
-	void *value4 = "Czwarta";
-	void *value5 = "Piąta";
-
-	void *retval = hashtable_set(h, "jeden", value1);
-	assert(retval == NULL);
-
-	void *found = hashtable_lookup(h, "jeden");
-	assert(found != NULL && !strcmp(value1, found));
-
-	retval = hashtable_set(h, "dwa", value2);
-	assert(retval == NULL);
-
-	retval = hashtable_set(h, "trzy", value3);
-	assert(retval == NULL);
-
-	retval = hashtable_set(h, "cztery", value4);
-	assert(retval == NULL);
-
-	retval = hashtable_set(h, "jeden", value5);
-	assert(retval != NULL);
-	assert (retval == value1);
-
-	retval = hashtable_lookup(h, "niema");
-	assert(retval == NULL);
-
-	retval = hashtable_lookup(h, "jeden");
-	assert(retval == value5);
-
-	ht_iterator iter = hashtable_iter(h);
-
-	while (ht_iter_next(&iter)) {
-		printf("Key %s, value: %s\n", ht_iter_key(&iter), (const char*) ht_iter_value(&iter));
-	}
-	
-	
-	retval = hashtable_remove(h, "cztery");
-	assert (retval == value4);
-	retval = hashtable_remove(h, "trzy");
-	assert(retval == value3);
-	retval = hashtable_remove(h, "dwa");
-	assert(retval == value2);
-	retval = hashtable_remove(h, "jeden");
-	assert(retval == value5);
-
-	hashtable_destroy(h);
-}
-
-int main() {
-   test_hashtable(2);
-   test_hashtable(10);
-}