Migrating gRPC Queries API reference from Slate (Iroha API) (hyperled…

…ger-iroha#1152)

* Add query section

Signed-off-by: neewy <[email protected]>

* Add small fixes

Signed-off-by: neewy <[email protected]>

* Add formatting fixes

Signed-off-by: neewy <[email protected]>

* Add a fix

Signed-off-by: neewy <[email protected]>

* Add a fix

Signed-off-by: neewy <[email protected]>

* Add a fix

Signed-off-by: neewy <[email protected]>

* Update with new stateless validation rules

Signed-off-by: neewy <[email protected]>

* Fix headings styles in queries documentation

Signed-off-by: Igor Egorov <[email protected]>

* Change links

Signed-off-by: neewy <[email protected]>