Add TMK file format support

[piotr-roslaniec]

Type of PR:

• Feature

Required reviews:

• 2

What this does:

• Adds encapsulated encryption to Enrico
• Adds TMK serialization format

Issues fixed/closed:

• Fixes #...

Why it's needed:

Explain how this PR fits in the greater context of the NuCypher Network.
E.g., if this PR address a nucypher/productdev issue, let reviewers know!

Notes for reviewers:

What should reviewers focus on?
Is there a particular commit/function/section of your PR that requires more attention from reviewers?

[codecov-commenter]

Codecov Report

Merging #254 (7e19676) into beta (ae56829) will increase coverage by 0.54%.
The diff coverage is 95.74%.

@@            Coverage Diff             @@
##             beta     #254      +/-   ##
==========================================
+ Coverage   83.66%   84.20%   +0.54%     
==========================================
  Files          37       37              
  Lines         967     1013      +46     
  Branches      121      129       +8     
==========================================
+ Hits          809      853      +44     
- Misses        152      153       +1     
- Partials        6        7       +1     

Files Changed	Coverage Δ
src/characters/enrico.ts	90.41% <95.55%> (+7.65%)	⬆️
src/utils.ts	97.95% <100.00%> (+0.08%)	⬆️

[cygnusv]

Do we need a TMK format after the changes in nucypher/ferveo#149 (and TBD changes in nucypher-core)?

[derekpierre]

Do we need a TMK format after the changes in nucypher/ferveo#149 (and TBD changes in nucypher-core)?

Yes. This is the goal of nucypher/nucypher#3194.

I think (?) this PR was created before as a stop gap measure, but it is unclear to me that this PR is needed or should be merged. @piotr-roslaniec ?

[piotr-roslaniec]

This PR was originally started 3 weeks ago, so perhaps it has outlived its usefulness. If we don't need to bridge the gap, I'd be okay with closing it.