GH-83: Add Firebase models and repositories

[TripleFrequency]

This is the first PR of many in regards to changes with Firebase. I am merging in stages as to keep the PRs down to a manageable size.

This adds the first stage, the lowest-level models used directly in Firebase, along with repositories for accessing them. In the future, this will be abstracted through a couple layers, allowing for far easier usage with the Places API and Firebase as one.

[codecov[bot]]

Codecov Report

Merging #87 into master will decrease coverage by 0.89%. The diff coverage is 0%.

@@            Coverage Diff             @@
##             master     #87     +/-   ##
==========================================
- Coverage      4.23%   3.34%   -0.9%     
  Complexity        4       4             
==========================================
  Files            24      34     +10     
  Lines           378     479    +101     
  Branches         35      38      +3     
==========================================
  Hits             16      16             
- Misses          360     461    +101     
  Partials          2       2

Impacted Files	Coverage Δ	Complexity Δ
...gry/firebase/repository/FirebasePlaceRepository.kt	0% <0%> (ø)	0 <0> (?)
...ry/firebase/repository/FirebaseReviewRepository.kt	0% <0%> (ø)	0 <0> (?)
...ngry/firebase/repository/FirebaseUserRepository.kt	0% <0%> (ø)	0 <0> (?)
...in/io/imhungry/firebase/model/user/FirebaseUser.kt	0% <0%> (ø)	0 <0> (?)
...o/imhungry/firebase/model/places/FirebaseReview.kt	0% <0%> (ø)	0 <0> (?)
...io/imhungry/firebase/model/places/FirebasePlace.kt	0% <0%> (ø)	0 <0> (?)
...io/imhungry/firebase/model/places/FirebaseVisit.kt	0% <0%> (ø)	0 <0> (?)
...gry/firebase/repository/FirebaseVisitRepository.kt	0% <0%> (ø)	0 <0> (?)
...rebase/model/user/privacy/FirebasePrivacyConfig.kt	0% <0%> (ø)	0 <0> (?)
...ase/repository/FirebaseBaseCollectionRepository.kt	0% <0%> (ø)	0 <0> (?)
... and 10 more

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