manifest: add features field

[fyrchik]

Close #1936 .

[codecov]

Codecov Report

Merging #1944 (bb039ef) into master (3acdbbd) will decrease coverage by 0.08%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master    #1944      +/-   ##
==========================================
- Coverage   82.73%   82.65%   -0.09%     
==========================================
  Files         290      290              
  Lines       23299    23304       +5     
==========================================
- Hits        19277    19261      -16     
- Misses       2792     2801       +9     
- Partials     1230     1242      +12     

Impacted Files	Coverage Δ
pkg/smartcontract/manifest/manifest.go	79.06% <60.00%> (-20.13%)	⬇️
pkg/network/server.go	70.73% <0.00%> (+0.14%)	⬆️
pkg/services/notary/notary.go	92.46% <0.00%> (+1.00%)	⬆️
pkg/services/oracle/request.go	48.92% <0.00%> (+1.43%)	⬆️

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[AnnaShaleva]

Has something happened with the tests?