* replace old Sentry client with the new SDK
* do not initialize Sentry SDK twice, correct panic processing
* account prefix for panics
* log errors with account context data
* tests
* linter fixes
* removed 1.18 from available versions
* new error collector & improvements for errors
* update golangci-lint, microoptimizations, linter fixes
* UseTLS10 method
* remove dead code
* add 1.17 to the test matrix
* fix for docstring
* split the core package symbols into the subpackages (if feasible)
* Clone() method in Localizer component allows to clone it just like LocalizationMiddleware does.
* RavenClientInterface contains all *raven.Client method, which allows external use without type casting.
* Tests and godoc fix for Go 1.15.