* Implement issues 2386: add synchronization in lite verify and change all Certify to Verify
* Replace make(chan struct{}, 0) with make(chan struct{})
* Parameterize memroy cache size and add concurrent test
* Refactor import order
* Vulnerability in light client proxy
When calling GetCertifiedCommit the light client proxy would call
Certify and even on error return the Commit as if it had been correctly
certified.
Now it returns the error correctly and returns an empty Commit on error.
* Improve names for clarity
The lite package now contains StaticCertifier, DynamicCertifier and
InqueringCertifier. This also changes the method receivers from one
letter to two letter names, which will make future refactoring easier
and follows the coding standards.
* Fix test failures
* Rename files
* remove dead code
