1. Add Button.qml
2. Modify main.qml
1. Add FlowControl Class
1. [Fix Error] commit Button.qml (miss commit)
2. [Document] commit QT application Spec
1. [UI] add add.qml
2. [UI] add delete.qml
3. [UI] add view.qml
1. [UI] modify add.qml
1. Add DatabaseManager Class
1. remove dummy include from databasemanager.h