LazyMutable should be exported to an external library

[paagamelo]

Some candidates for an external library are:

• LazyMutable class, it allows to have a lazy initialised var (differs from a lateinit var because the client can specify an initialiser which is called lazily). It's not thread safe, when exporting it to a library a thread safe version should be implemented as well;
• RangeExtensions, along with their tests;
• IntersectionUtils, these are dependent on Alchemist geometry abstractions (e.g. vectors, segments), exporting them may be a thorny issue.