* support for count and aggregations on columns, close#786
* support explain query for aggregations
* '<arr-rel>_agg' in '<table>' type, fix order by for aggregations
* add 'allow_aggregations' key in select permissions
* Add checkbox to toggle count and aggregations on columns on select permission
* align aggregation checkbox with columns div
* improve readability of the generated sql
* alias is needed at the top level aggregation
* throw internal errors for unexpected fields
* rename SelFld to more readable TableAggFld
* rename agg to aggregate
Better SQL generation for select queries (the query plans will be the same but much more readable). This closes some long standing issues (#6, #121, #278).
* fix primary key changing on upsert, fix#342
* add 'update_columns' in 'on_conflict' object, consider 'allowUpsert'
* 'ConflictCtx' type should respect upsert cases
* validation for not null fields in an object
* filter schema identifiers to conform to graphql naming scheme,closes #134
Filter out tables, columns, relationships etc which does not conform to
graphql naming scheme.
This ensures GraphiQL initialisation works properly for existing
databases.
* rename `isGraphQLConform` to `isValidName`
* rename all graphQL validators
* add 'on_conflict' condition to allow upsert mutation, closes#105
* check for empty unique or primary key constraints
* add 'on_conflict' condition test cases and introspection test case
* update 'conflict_action' enum values' description
