Changed the names of the files to conform the python convection and also added photo_in_entry.py to diminish the cyclic import error in pylint

src/pilgrim/models/photo_in_entry.py

@@ -0,0 +1,8 @@
+from sqlalchemy import Table, Column, Integer, ForeignKey
+
+from ..database import Base
+
+photo_entry_association = Table('photo_entry_association', Base.metadata,
+Column('id', Integer, primary_key=True, autoincrement=True),
+    Column('fk_Photo_id', Integer, ForeignKey('photo.id')),
+    Column('fk_Entry_id', Integer, ForeignKey('Entry.id')))