Various cleanups

[fredroy]

Based on

• Execute regression test(s) for BeamAdapter scenes on Github Actions #28

(nice to check regression for every commit)

• Replace beginEdit/endEdit with writeAcessor
• Remove using namespace and make it explicit with vector is used (std:: or type:: ???)
• Remove one useless specialized function
• Remove warnings about conversion from int to unsigned (or float??)
• Remove one weird use of indices as float (??)
• Change NULL to nullptr
• use checkEventType instead of a dyn_cast
• clean dtors
• remove useless templatename
• etc....