Backport: Refactor + improve docs (#305)

- kinda revert the change from #304 where all collections inherit from `list` - there is now a new base class `MultiClusterMap`, which acts as a dict but is capable of holding data from multiple clusters (for example when querying database jobs from multiple clusters in pyslurm.db.Jobs)
- improve docs

Author: tazend

docs/reference/config.md

@@ -7,4 +7,3 @@ title: Config
     removed in the future when a replacement is introduced
 
 ::: pyslurm.config
-    handler: python

docs/reference/constants.md

@@ -3,5 +3,3 @@ title: constants
 ---
 
 ::: pyslurm.constants
-    handler: python
-

docs/reference/db/cluster.md

@@ -7,4 +7,3 @@ title: Cluster
     removed in the future when a replacement is introduced
 
 ::: pyslurm.slurmdb_clusters
-    handler: python

docs/reference/db/connection.md

@@ -3,4 +3,3 @@ title: Connection
 ---
 
 ::: pyslurm.db.Connection
-    handler: python

docs/reference/db/event.md

@@ -7,4 +7,3 @@ title: Event
     removed in the future when a replacement is introduced
 
 ::: pyslurm.slurmdb_events
-    handler: python

docs/reference/db/job.md

@@ -7,7 +7,4 @@ title: Job
     will be removed in a future release
 
 ::: pyslurm.db.Job
-    handler: python
-
 ::: pyslurm.db.Jobs
-    handler: python

docs/reference/db/jobfilter.md

@@ -3,4 +3,3 @@ title: JobFilter
 ---
 
 ::: pyslurm.db.JobFilter
-    handler: python

docs/reference/db/jobstats.md

@@ -3,4 +3,3 @@ title: JobStatistics
 ---
 
 ::: pyslurm.db.JobStatistics
-    handler: python

docs/reference/db/jobstep.md

@@ -3,7 +3,4 @@ title: JobStep
 ---
 
 ::: pyslurm.db.JobStep
-    handler: python
-
 ::: pyslurm.db.JobSteps
-    handler: python

docs/reference/db/reservation.md

@@ -7,4 +7,3 @@ title: Reservation
     removed in the future when a replacement is introduced
 
 ::: pyslurm.slurmdb_reservations
-    handler: python