Implement Virtual Filesystem

[AldaronLau]

• Implement Ember::new(size: usize) -> Self (creates file representing filesystem)

• Implement Ember::save(&mut self, data: &[u8], tags: &Tags) -> Result<(), Error>

• Implement Ember::find(&mut self, filters: &Filters, tag_kind: u8, fuzzy_search: &str) -> impl Iterator<Item = Metadata>

• Implement Ember::load(&mut self, file_id: &FileId)

• Implement struct FileId(u64)

• Implement struct Tag { kind: u8, name: &str }

• Implement Tags::new()

• Implement Tags::add(self, tag: &Tag) -> Self

• Implement enum Metadata { Tag { tag: Tag }, File { file_id: FileId, .... }) }

• Implement Filters::new()

• Implement Filters::add(self, tag: Tag) -> Self