Add documentation for pallet_assets (#78)

* Add documentation for `pallet_assets`

* add info about `config`, `events` and `errors`

docs/modules/ROOT/pages/glossary.adoc

@@ -16,6 +16,10 @@ Asset Teleportation is a movement of an asset by destroying it on one side and c
 
 A generic filter which returns whether or not XCM may pass and be executed. If they do not pass the barrier, they are not executed. The barrier is the final filter before XCM execution. It implements the `ShouldExecute` trait and therefore takes as input an XCM and returns a bool indicating whether it should be executed.
 
+=== Burning
+
+The process of destroying existing assets.
+
 == C
 
 === Candidacy Bond
@@ -55,6 +59,10 @@ Delegator is an account that granted call execution rights with <<proxy>> creati
 
 An asset where any unit of it worth the same. Opposite of <<nonfungible_asset>>
 
+=== NonFungible Asset
+
+An asset meaning that it is not interchangeable with other assets of the same type. For example, a non-fungible asset could be an NFT, while a fungible asset could be a currency token.
+
 == H
 
 === Hold 
@@ -93,6 +101,10 @@ Nearly the same as `<<Hold>>`, with 2 major differences:
 
 == M
 
+=== Minting
+
+The process of creating new assets.
+
 === MultiAsset
 
 Either an amount of a single fungible asset, or one non-fungible asset.
@@ -137,6 +149,10 @@ When consensus systems do not have a established layer of trust over which they
 
 == T
 
+=== Thawing
+
+The process of unfreezing an asset after being frozen.
+
 === Tip
 
 An optional tip. Tip increases the priority of the transaction, giving it a higher chance to be included by the transaction queue.