* (refactor) change all sql references of user_password to username_password
* refactor(pkg) renamed pkg userpassword to usernamepassword
* refactor(proto) updated protocol buffers to use UsernamePassword
* refactor(code) updated references from UserPassword to UsernamePassword in golang files
* refactor(test) updated unit tests to reference UsernamePassword changes
* refactor(ddtest) updated references in dbtests to use UsernamePassword
* chore(sql-test) fixed spelling issue
* chore(sql) added and updated comments in migartion & tables. fixed indentations
* chore(proto) updated comments to reflect username_password changes
* refactor(tests) updated unit tests to replace user-password with username-password
* refactor(cmd) updated cmd help text to use username
* chore(tests) update test name & comments
* fix(cmd) fixed cmd usage definition for credentials update
* refactor(tests) removed out of scope changes
* fix(sql) incremented sql migration id & updated migration comments
Damian Debkowski
Louis Ruch