Postgres Data Source (#9475)

* add postgresql datasource

* add rest of files for postgres datasource

* fix timeseries query, remove unused code

* consistent naming, refactoring

* s/mysql/postgres/

* s/mysql/postgres/

* couple more tests

* tests for more datatypes

* fix macros for postgres

* add __timeSec macro

* add frontend for postgres datasource

* adjust documentation

* fix formatting

* add proper plugin description

* merge editor changes from mysql

* port changes from mysql datasource

* set proper defaultQuery for postgres

* add time_sec to timeseries query
accept int for value for timeseries query

* revert allowing time_sec and handle int or float values as unix
timestamp for "time" column

* fix tslint error

* handle decimal values in timeseries query

* allow setting sslmode for postgres datasource

* use type switch for handling data types

* fix value for timeseries query

* refactor timeseries queries to make them more flexible

* remove debug statement from inner loop in type conversion

* use plain for loop in getTypedRowData

* fix timeseries queries

* adjust postgres datasource to tsdb refactoring

* adjust postgres datasource to frontend changes

* update lib/pq to latest version

* move type conversion to getTypedRowData

* handle address types cidr, inet and macaddr

* adjust response parser and docs for annotations

* convert unknown types to string

* add documentation for postgres datasource

* add another example query with metric column

* set more helpful default query

* update help text in query editor

* handle NULL in value column of timeseries query

* add __timeGroup macro

* add test for __timeGroup macro

* document __timeGroup and set proper default query for annotations

* fix typos in docs

* add postgres to list of datasources

* add postgres to builtInPlugins

* mysql: refactoring as prep for merging postgres

Refactors out the initialization of the xorm engine and the query logic
for an sql data source.

* mysql: rename refactoring + test update

* postgres:refactor to use SqlEngine(same as mysql)

Refactored to use a common base class with the MySql data source.

Other changes from the original PR:
- Changed time column to be time_sec to allow other time units in the
future and to be the same as MySQL
- Changed integration test to test the main Query method rather than
the private transformToTable method
- Changed the __timeSec macro name to __timeEpoch
- Renamed PostgresExecutor to PostgresQueryEndpoint

Fixes #9209 (the original PR)

* postgres: encrypt password on config page

With some other cosmetic changes to the config page:
- placeholder texts
- reset button for the password after it has been encrypted.
- default value for the sslmode field.

* postgres: change back col name to time from time_sec

* postgres mysql: remove annotation title

Title has been removed from annotations

* postgres: fix images for docs page

* postgres mysql: fix specs

public/app/plugins/datasource/postgres/module.ts

@@ -0,0 +1,43 @@
+///<reference path="../../../headers/common.d.ts" />
+
+import {PostgresDatasource} from './datasource';
+import {PostgresQueryCtrl} from './query_ctrl';
+
+class PostgresConfigCtrl {
+  static templateUrl = 'partials/config.html';
+
+  current: any;
+  constructor($scope) {
+    this.current.jsonData.sslmode = this.current.jsonData.sslmode || 'require';
+  }
+}
+
+const defaultQuery = `SELECT
+  extract(epoch from time_column) AS time,
+  title_column as title,
+  description_column as text
+FROM
+  metric_table
+WHERE
+  $__timeFilter(time_column)
+`;
+
+class PostgresAnnotationsQueryCtrl {
+  static templateUrl = 'partials/annotations.editor.html';
+
+  annotation: any;
+
+  /** @ngInject **/
+  constructor() {
+    this.annotation.rawQuery = this.annotation.rawQuery || defaultQuery;
+  }
+}
+
+export {
+  PostgresDatasource,
+  PostgresDatasource as Datasource,
+  PostgresQueryCtrl as QueryCtrl,
+  PostgresConfigCtrl as ConfigCtrl,
+  PostgresAnnotationsQueryCtrl as AnnotationsQueryCtrl,
+};
+