handle case insensitive username
wire up for mac
add tests for new token look up code
update test name
add a comment for the new find routine
refacotring on existing token cache implementations
add logic to normalize user id
add a factory method
Merge branch 'dev' into username
fix a bug using a wrong token storage variable name
fix an issue that we miss a token on saving to disk
rename file to better names
remove invalid tests
add new tests for token cache
Merge pull request #1365 from yugangw-msft/username

azure login token caching should support case insensitive user name