Changed elasticsearch AR primary key handling

now supports mapped primary key when _id is part of source with an
alias.
tests improved, verify added
Fixes #1827: Debugger toolbar is loaded twice if an action is calling `run()` to execute another action
Fixes #1835: `CheckboxColumn` now renders checkboxes whose values are the corresponding data key values
updated extension changelog.
UplodedFile enhasement
default values for db\Connection username and password to null

fixes #1821
UplodedFile enhasement
UplodedFile enhasement
UplodedFile enhasement
Advanced app template: moved database connection DSN, login and password to -local config not to expose it to VCS
Adjusted advanced application template docs to reflect DB config movement
Added readme line for advanced app change
Fixes #1633: fixed scenarios for User model in advanced application allowing setting default values for User model
Added link to ICU Locale docs in order to clarify what are Yii::$app->language values
Removed translations for messages intended for developers
Improved plural messages for validators
Added guide for contributing message translations
Added message translations for Russian
Fixes #1846