lightningd: move basic parameter parsing into common/configdir

lightning-cli is going to need to know what network we're on, so
it will need to parse the config files.  Move the code which does
the initial bootstrap parsing into common, as well as the config
file parsing core.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

cli/test/run-remove-hint.c

@@ -114,6 +114,7 @@ int main(int argc UNUSED, char *argv[])
 
 	output = tal_strdup(NULL, "");
 	assert(test_main(3, fake_argv) == 0);
+	assert(!taken_any());
 
 	assert(streq(output, "channels=\n"
 		     "\n"
@@ -129,5 +130,6 @@ int main(int argc UNUSED, char *argv[])
 		     "num_channels=1\n"
 		     "num_connected=1\n"));
 	tal_free(output);
+	take_cleanup();
 	return 0;
 }