delete layout and useraccount tables, rename main_router to pride_router

[colin-combe]

@sureshhewabi - first part of the changes we just discussed:

• delete layout table
• delete useraccounttable
• rename main_router to pride_router
• rename main.py to pride.py

main.py will become place for a small amount of code that's shared by all the APIs (PRIDE, PDBdev & xiVIEW data loader)

[colin-combe]

I don't know why the GH interface isn't letting me assign reviewers, i would if it let me...

[colin-combe]

@sureshhewabi - actually, i think 'shared.py' might be a better name than 'main.py' for the new file