Adding Basic Private Key Management (#671)

* adding flags

* adding modified key utils

* adding more funcs

* more changes

* more changes

* documentation

* changes to node

* gazelle

* fixing bazel build

* gazelle

* adding tests

* more tests

* addressing terence's feedback

* adding geth header

* test

* changes

* fixedd it

* fixed marshalling

* adding more to tests

* gazelle

* adding more tests

* lint

* add cov

* cov

* fix imports

.codecov.yml

@@ -11,7 +11,7 @@ coverage:
     project: 
       default:
         target: auto
-        threshold: 1%
+        threshold: 1.5%
     patch: no
     changes: no