Hao-Hsiang Song / topics-auction

Fix UserID String -> long

Add API list
Remove userId from constructor

Merge branch 'master' of mit.cs.uchicago.edu:haohsiang/topics-auction

# Conflicts:
#	target/h2db.mv.db

# Conflicts:
#	target/h2db.mv.db

Change item status to SOLD when checkout

- Set H2 database to persistence mode (db is saved to target/h2db); data added to db will not disappear after stopping the program
- H2 database can now be viewed at http://localhost:8080/h2-console (JDBC URL:jdbc:h2:file:./target/h2db)
- Add feature adding item to cart; cart, with the same id as user's, automatically create when adding item to cart
- Comment out User and related classes for now

# Conflicts:
#	.gitignore

# Conflicts:
#	.gitignore
#	target/classes/application.properties
#	target/classes/edu/uchicago/mpcs/topics/auction/Bid.class
#	target/classes/edu/uchicago/mpcs/topics/auction/Item.class
#	target/classes/edu/uchicago/mpcs/topics/auction/ItemCategory.class
#	target/classes/edu/uchicago/mpcs/topics/user/User.class

# Conflicts:
#	.gitignore
#	src/main/java/edu/uchicago/mpcs/topics/Application.java
#	src/main/java/edu/uchicago/mpcs/topics/controller/UserController.java
#	src/main/java/edu/uchicago/mpcs/topics/db/UserDB.java
#	src/main/java/edu/uchicago/mpcs/topics/service/UserService.java
#	src/main/java/edu/uchicago/mpcs/topics/user/CustomerSupport.java
#	src/main/java/edu/uchicago/mpcs/topics/user/User.java