implement Help command.
fix bugs while read UTF-8 text file.
refactor Insolvency function.
modify some prompt message.
move UIException to Application package and rename it to GameException.
move Quit to PropSelectorFactory class.
fix bugs in GiftHouse.
extract methods in class.
rename functions.
add argument check.
fix some code inspection results.
Merge branch 'dev' of github.com:itZhy/Rich into dev

Conflicts:
	src/main/java/Estate/Vacancy.java
	src/main/java/Player/Rounder.java