Feature handle new local files

[ThunderKey]

Tested with:

• Removing the cache file: rm ~/.local/share/kitovu/filecache.json
• Changing a file
• kitovu sync
• Everything has the state FileState.NO_CHANGES and does nothing (but update teh filecache)
• One Exception is the edited file which has FileState.BOTH_CHANGED and gets downloaded

Maybe we could make the filecache.File class wrapping local_digest and remote_digest. We then could move the _compare_digests to that class as well instead of having the FileCache do everything

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@e523d39). Click here to learn what that means. The diff coverage is 28.57%.

@@            Coverage Diff            @@
##             master      #30   +/-   ##
=========================================
  Coverage          ?   90.99%           
=========================================
  Files             ?       32           
  Lines             ?     1310           
  Branches          ?       85           
=========================================
  Hits              ?     1192           
  Misses            ?      105           
  Partials          ?       13

Impacted Files	Coverage Δ
src/kitovu/sync/filecache.py	89.85% <28.57%> (ø)

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[The-Compiler]

LGTM now!

[The-Compiler]

Oh, something I forgot: It'd be nice to add a test for this...

[ThunderKey]

Added tests in #35