2. Ensure backup should work with '--data-only' and '--schema-only' for any format. Fixes#3347
3. Added supported "Dump Options" for "pg_dumpall" which was not there since pgAdmin 3.
4. Fixed issue where "--clean" should not clubbed with "--data-only" while taking backup.
5. Fixed "--oids" should not clubbed with "--inserts" or "--column-inserts" while taking backup.
As sessions in pgAdmin4 are filesystem based session, they need locking
for avoiding the access from multiple threads, specially running as an
WSGI application.
Fixes#3547
Akshay Joshi
Harshal Dhumal
Usman Muzaffar
Aditya Toshniwal
Joao De Almeida Pereira
Isaias Sanchez