* add a query to reload schema cache (metadata), close hasura#292

* minor code refactor

* simpler root level select fields using primary keys (fix hasura#304) (hasura#306)

* select fields by primary key col values as argument values, fix hasura#304

* change field name 'table_by_pkey' to 'table_by_pk'

* add links to share and help (hasura#303)

* add req_user_id as alias to x-hasura-user-id (fix hasura#317) (hasura#320)

* fix insert fails for non-admin roles on v1/query  (fix hasura#327) (hasura#328)

* fix insert fails for non-admin roles on v1/query, fix hasura#327

* add test case for user role upsert usint constraint name

* mutation return type and query type are same (close hasura#315) (hasura#324)

* add support for jwt authorization (close hasura#186) (hasura#255)

The API:
1. HGE has `--jwt-secret` flag or `HASURA_GRAPHQL_JWT_SECRET` env var. The value of which is a JSON.

2. The structure of this JSON is: `{"type": "<standard-JWT-algorithms>", "key": "<the-key>"}`
`type` : Standard JWT algos : `HS256`, `RS256`, `RS512` etc. (see jwt.io).
`key`:
  i. Incase of symmetric key, the key as it is.
  ii. Incase of asymmetric keys, only the public key, in a PEM encoded string or as a X509 certificate.

3. The claims in the JWT token must contain the following:
  i. `x-hasura-default-role` field: default role of that user
  ii. `x-hasura-allowed-roles` : A list of allowed roles for the user. The default role is overriden by `x-hasura-role` header.

4. The claims in the JWT token,  can have other `x-hasura-*` fields where their values can only be strings.

5. The JWT tokens are sent as `Authorization: Bearer <token>` headers.

---
To test:
1. Generate a shared secret (for HMAC-SHA256) or RSA key pair.
2. Goto https://jwt.io/ , add the keys
3. Edit the claims to have `x-hasura-role` (mandatory) and other `x-hasura-*` fields. Add permissions related to the claims to test permissions.
4. Start HGE with `--jwt-secret` flag or `HASURA_GRAPHQL_JWT_SECRET` env var, which takes a JSON string: `{"type": "HS256", "key": "mylongsharedsecret"}` or `{"type":"RS256", "key": "<PEM-encoded-public-key>"}`
5. Copy the JWT token from jwt.io and use it in the `Authorization: Bearer <token>` header.

---
TODO: Support EC public keys. It is blocked on frasertweedale/hs-jose#61

* compare only major and minor versions for cli-server (fix hasura#331) (hasura#332)

* Revert "add links to share and help (hasura#303)" (hasura#334)

This reverts commit 798efdd.

* update tests to use access key (close hasura#113) (hasura#296)

Closes hasura#113

* generate a returning field in a mutation only when the select permission is defined (fix hasura#340) (hasura#341)

* allow selectively updating columns on a conflict during insert (fix hasura#342)

* fix primary key changing on upsert, fix hasura#342

* add 'update_columns' in 'on_conflict' object, consider 'allowUpsert'

* 'ConflictCtx' type should respect upsert cases

* validation for not null fields in an object

* console: fix error notification non json, auto height css (hasura#354)

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