Delete cards feature

Added a JCheckBox to CardDetailsPanel while the user is in editing mode.
User first needs to find the appropriate cards and then while in editing
mode, using checkbox, mark the desired cards for removal. Upon clicking
on 'Done' button, records of selected cards are removed from the
database.
Delete cards feature, delete button + dialog

Added an additional button which enables user to delete marked cards or
the current card if no cards are marked. A confirm dialog is opened upon
clicking on button, warning user before deleting cards. The view is
updated after deleting cards, allowing user to continue editing cards.
Delete cards feature, corrections

Corrected indentation and whitespace issues.
Delete cards feature, frame adjustments

Moved the checkbox under "Player details" panel, whitespace+indentation
corrections, checkbox is disabled when in "Add cards" mode to maintain
the frame size.
Delete cards feature, frame size

The frame size should be consistent now.
Merge pull request #2 from tmatek/ticket107

Delete cards feature