Handle shared dependencies being required by server dependencies

[ddavness]

Not really the best title to this PR. Fixes #66

[ddavness]

Note to self - when developing on Windows make sure that the encoding of files isn't set to UTF16-LE 😬

[ddavness]

At this point two integration tests were added:

• cross-realm-dependency - A shared project which requires a server dependency A which in turn requires a shared dependency B. It is expected to FAIL on v0.3.1

• cross-realm-explicit-dependency - A shared project which explicitly requires A (server) and B (shared) - A also requires B. It PASSES on v0.3.1

[ddavness]

In a nutshell (I think):

• The resolution process will now tag all dependencies of a server dependency as belonging to the server realm of the project UNLESS one or more of these dependencies is required by a dependency on the shared realm - in that case those dependencies will be moved to the shared realm instead;
• One unit test was fixed to verify the behavior, and another one was added as a counter-example;
• Two integration tests were added to confirm the behavior;
• One of the tests is failing at the moment because the lockfile implementation doesn't seem complete yet;

[magnalite]

Amazing work on this! I have no comments and agree with all your changes. Lockfiles are now generated correctly (#130) so this is ready to be merged! I have updated the snap files to respect these full lockfiles correctly. Thanks for putting this together and sorry it took so long to merge.