Enhancement/add documentation

[cstrangedk]

• Added in-line documentation to delegation contracts
• Added SPDX License ID

[codecov]

Codecov Report

Merging #239 into develop will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #239   +/-   ##
========================================
  Coverage    94.80%   94.80%           
========================================
  Files           33       33           
  Lines         2463     2463           
  Branches       342      342           
========================================
  Hits          2335     2335           
  Misses         128      128           

Impacted Files	Coverage Δ
contracts/ConstantsHolder.sol	87.09% <ø> (ø)
contracts/ContractManager.sol	100.00% <ø> (ø)
contracts/Decryption.sol	100.00% <ø> (ø)
contracts/ECDH.sol	96.29% <ø> (ø)
contracts/GroupsData.sol	91.66% <ø> (ø)
contracts/GroupsFunctionality.sol	75.60% <ø> (ø)
contracts/MonitorsData.sol	100.00% <ø> (ø)
contracts/MonitorsFunctionality.sol	99.29% <ø> (ø)
contracts/Nodes.sol	98.75% <ø> (ø)
contracts/Permissions.sol	78.57% <ø> (ø)
... and 23 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e2abc09...7f5fb34. Read the comment docs.

[payvint]

Good!