This subforum is to post hacks, but anyway

A map editor - Advance Map
A tool to add all 649 Pokemon - it doesn't exist
An event editor - We call it a script editor. XSE and PKSV-UI are good.
A tool to change which Pokemon appear where - You can do this in advance map
A tool for adding legendaries to scenary - You can put them in a map, using Advance map
A tool for changing which Pokemon trainers use - I think this is done using PET
A tool for adding trainers - EDIT: It doesn't exist