Added code and test for token cache clear()
Implemented clear method on token store for unix.
Implement win-token-storage.clear
- Added unit tests

Signed-off-by: stankovski <denis.stankovski@gmail.com>
Implement osx-token-storage.clear
- Add unit tests
Clear token cache as part of cmd account clear
Enable rest of the tests
Fixed missing require and test name
Test fix for node 0.8
Merge pull request #1410 from christav/token-cache-clear

Clear token cache when doing azure account clear