Additional Unit Tests, Refactoring, & C FFI Pointer Validation

[mmstick]

There should be no changes to functionality or the API made in this PR. Functionality only needs to be tested to ensure that everything still works as before. GTK installer + CLI

• Fix a build error due to a lack of a dev dependency for an example
• Fix an existing test which is broken
• Add many more unit tests for that which is not yet unit tested
• Refactor BlockInfo
• Add a few function comments missing from PartitionInfo's methods.
• Applied clippy suggestions, which will improve performance
• Refactored the CLI workspace into modules
• Check every pointer received from the C FFI before attempting to do anything with them.

Closes #45

[mmstick]

The clippy bug that distinst's source code uncovered yesterday was fixed today, so I'll soon submit another clippy commit.

[brs17]

Had an installation fail on me when installing with these patches.

Logs from installer:
ERROR: bootloader error: nul byte found in provided data
installerlogs.log

journald logs:
journaldlogs.log

[mmstick]

@brs17 I think that issue is affecting master at the moment. Thought I had fixed it. Seems to happen at random, because something (I'm assuming Vala) is freeing some statically-initialized memory that distinst wants to reuse.

Short-term, I may hand Vala a unique copy of the data so it won't also end up eating the hand that feeds it in the process.

[brs17]

Looks like while it said installation failed, it actually worked.

Huh, interesting, I'm going to give this pr another go.

[mmstick]

About to submit a commit that should fix the issue for now.

[brs17]

Tried the latest from this pr. After updating, initially the installer did not run when I selected it. Selecting it a second time, it launched and installed just fine. Only oddity I noticed was the titlebar:

[mmstick]

I know what's wrong. Submitting a fix soon.

[mmstick]

@brs17 You should be able to try again soon.

[brs17]

Looks good from a "it doesn't break stuff" viewpoint.