Feature/immutable-crypto-conditions

[sappenin]

This PR introduces immutable Conditions and Fulfillments. Previously, many of the internals of each Condition and Fulfillment contained data that was lazily-loaded or initialized. Because of this mutability, certain thread-safety aspects of the code base were in doubt. Additionally, equals/hashcode implementations were sometimes difficult to make consistent because they were often based upon lazily initialized data (equals/hashcode/toString is often called anyway throughout the course of using a Condition or Fulfillment, so the lazy optimizations were likely not adding value in many cases anyway).

After performing some basic timing tests against the 0.2.0-SNAPSHOT construction and encoding times vs the time taken to preemptively compute things like fingerprints (the model used in this PR), there isn't much of a performance savings gained by lazily computing certain pieces of information. Thus, this proposed implementation removes this in favor of final attributes in each class.

This PR includes the following additional changes, and also addresses #66, #61, #59, #57, #55, #54,#47, and #43.

• Update code to support crypto-conditions spec draft-03 (bumped project version to 0.0.3-SNAPSHOT)
• Update all conditions and fulfillments to be immutable.
• Fix .equals() and .hashcode() for all conditions and fulfillments.
• Enhance TestVector coverage for all conditions and fulfillments.
• Enable parameterized RSA signature tests (this is a test vector from the JS implementation found here that was not previously tested in the Java lib).
• Limit Guava to test scope only.
• Cleanup Javadoc and imports and fix all Checkstyle errors.
• Remove unused code and test classes.
• Address TODOs comments throughout the code.
• Update README.

[codecov[bot]]

Codecov Report

Merging #68 into development will increase coverage by 31.52%. The diff coverage is 65.54%.

@@                Coverage Diff                 @@
##             development      #68       +/-   ##
==================================================
+ Coverage          37.89%   69.41%   +31.52%     
- Complexity            97      206      +109     
==================================================
  Files                 24       25        +1     
  Lines                863     1030      +167     
  Branches              86      116       +30     
==================================================
+ Hits                 327      715      +388     
+ Misses               507      256      -251     
- Partials              29       59       +30

Impacted Files	Coverage Δ	Complexity Δ
...erledger/cryptoconditions/der/DerOutputStream.java	100% <ø> (+36.36%)	8 <0> (ø)	:arrow_down:
...ger/cryptoconditions/utils/UnsignedBigInteger.java	50% <ø> (ø)	2 <0> (?)
...erledger/cryptoconditions/NamedInformationUri.java	87.75% <ø> (ø)	12 <0> (?)
...ledger/cryptoconditions/CryptoConditionReader.java	79.62% <100%> (ø)	20 <0> (?)
...dger/cryptoconditions/PreimageSha256Condition.java	100% <100%> (ø)	4 <3> (?)
...rg/interledger/cryptoconditions/ConditionBase.java	33.33% <25.92%> (-16.67%)	5 <5> (-1)
...dger/cryptoconditions/PrefixSha256Fulfillment.java	36.36% <36.36%> (ø)	6 <6> (?)
...rledger/cryptoconditions/RsaSha256Fulfillment.java	38.29% <38.29%> (ø)	6 <6> (?)
...ger/cryptoconditions/Ed25519Sha256Fulfillment.java	38.29% <38.29%> (ø)	5 <5> (?)
...r/cryptoconditions/ThresholdSha256Fulfillment.java	39.13% <39.13%> (ø)	7 <7> (?)
... and 25 more

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