Add SNEWSMessage class hierarchy.

docs/user/firedrills.md

@@ -44,24 +44,24 @@ We would like to test two main interactions; **subscribing**  & **publishing** t
 
 - API:
     ```python
-     from snews_pt.snews_pub import SNEWSTiersPublisher
-     SNEWSTiersPublisher(detector_name='KamLAND', 
+     from snews_pt.messages import SNEWSMessageBuilder
+     SNEWSMessageBuilder(detector_name='KamLAND', 
                          neutrino_time="2022-02-28T04:31:08.678999",
                          p_val=0.000007,
                          machine_time="2022-02-28T04:31:09.778859", 
                          firedrill_mode=True,
                          is_test=True,
-                         ).send_to_snews()
+                         ).send_messages()
     ```
-  or 
+  or
   ```python
-  from snews_pt.snews_pub import SNEWSTiersPublisher
-  observation = SNEWSTiersPublisher.from_json('somejsonfile.json', 
+  from snews_pt.messages import SNEWSMessageBuilder
+  observation = SNEWSMessageBuilder.from_json('somejsonfile.json', 
                                               detector_name='XENONnT',
                                               firedrill_mode=True,
                                               is_test=True, 
                                               comment="This is submitted from a json file")
-  observation.send_to_snews()
+  observation.send_messages()
   ```
 Notice that `SNEWSTiersPublisher` returns an object which actually contains the decided tiers, and formatted messages. 
 One can play with this object before finally `send_to_snews()`.  

docs/user/publishing_protocols.md

@@ -18,10 +18,12 @@ The user can share as much information as they desire with one simple function c
 sets the "Tier" and any additional information is passed under `meta` field.
 
 The user can use `SNEWSTiersPublisher` to create observation message(s) and send them to snews.
+
 ```python
-from snews_pt.snews_pub import SNEWSTiersPublisher
-messages = SNEWSTiersPublisher(neutrino_time="2022-02-28T04:31:08.678999")
-messages.send_to_snews()
+from snews_pt.messages import SNEWSMessageBuilder
+
+messages = SNEWSMessageBuilder(neutrino_time="2022-02-28T04:31:08.678999")
+messages.send_messages()
 ```
 User can also investigate their messages before sending it to SNEWS. The `SNEWSTiersPublisher` creates an object which contains 
 the generated and formatted messages. It can also tell you what "Tiers" are selected based on the input that is given. 
@@ -92,7 +94,7 @@ Notice that your message can contain fields that correspond to several tiers e.g
 In the example below `SNEWSTierPublisher` creates a message for "CoincidenceTier" because the `neutrino_time` is passed, and it creates 
 another message for the "Significance Tier" because the `p_values` together with the `t_bin_width` is passed. 
 
-Here the `p_val` is the p value of the detection and it is optional. The `detector_name` can be passed manually, however, if the name is initially set, this is also not needed.
+Here the `p_val` is the p value of the detection, and it is optional. The `detector_name` can be passed manually, however, if the name is initially set, this is also not needed.
 
 <img src="../example_publishing.png" alt="Publication example" width="2000"/>