Adding compressed public key flag to java api #443

1. 
   Christewart commented at 9:43 pm on February 21, 2017: none

   Implements the ability to generate a compressed public key from the java API.
2. 
   Christewart commented at 10:20 pm on February 21, 2017: none

   Could this build failure from buffer sizes being fixed 65 byte constants?

   https://github.com/Christewart/secp256k1/blob/4ef814c3cc25dea55389f3fb2c74536abc82d148/src/java/org_bitcoin_NativeSecp256k1.c#L294-L296

3. Christewart cross-referenced this on Mar 22, 2017 from issue Adding new secp256k1 functionality by Christewart
4. Adding flag to generate compressed public key for java api

   Fixing a few checkInvariants
   
   Adding compressed flag to tweak_mul and tweak_add
   
   Fixing some nits

   c365395d96
5. Exposing secp256k1 parsepubkey functionality via `isValidPubKey` method

   Exposing secp256k1 parse pubkey functionality in the java api
   
   Fixing some nits, refactoring some code
   
   Changing name of method from 'parsePubKey' to 'isValidPubKey'
   
   Removing compressed flag arg from 'isValidPubKey' method

   2375636d67
6. Christewart force-pushed on Mar 23, 2017
7. 
   Christewart commented at 1:02 pm on April 18, 2017: none

   I added a little more functionality, there is now a isValildPubKey method that calls the underlying ec_pubkey_parse. I’d also like to eventually remove the guava dependency. I removed the Preconditions.checkArgument code and create our version called checkInvariant().
8. Christewart cross-referenced this on Mar 8, 2018 from issue Implement `decompress` function in JNI by pm47
9. Christewart closed this on Mar 11, 2018

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10. 
    Christewart commented at 6:06 pm on March 11, 2018: none

    superseded by #508

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