Mutable datatypes in podio@0.14.1 and later

Update CMakeLists.txt

Bump version number

Support eic::Index to be used as map key value

Specialized ProtoClusterHit structure

 - better readibility for protoclusters
 - now also store raw hit index to make navigation from protocluster-hit
   easier

Add data structure to store relational info for cluster mergin

Use Weight class for event weight

Merge branch '12-update-rich-data-structures' into 'master'

Resolve "Update RICH data structures"

Closes #12

See merge request EIC/eicd!43

Merge branch 'add_clusterID' into 'master'

Add clusterID to Clusters

See merge request EIC/eicd!31

Merge branch 'imaging_cluster' into 'master'

Change array of layers to OneToManyRelation between ImagingCluster and ImagingLayer

See merge request EIC/eicd!26