Use named imports across all Compact contracts

[0xisk]

Currently, modules are imported without named imports

import "../security/Initializable" prefix Initializable_;
// usage:
Initializable_initialize();
Initializable_assertInitialized();

We should explore using named imports instead, which would be more explicit and idiomatic:

import { initialize, assertInitialized } from "../security/Initializable";
// usage:
Initializable_initialize();
Initializable_assertInitialized();

Originally posted by @emnul in #190 (comment)