Add view for concerts

[hj235]

• Created list Ui components similar to those of Person list
• The two lists are fitted together using a HBox
• Also added getFilteredConcertList methods to logic classes, as well as the relevant test

Fixes #59

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 4.54545% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c/main/java/seedu/address/ui/ConcertListPanel.java	0.00%	12 Missing :warning:
src/main/java/seedu/address/ui/ConcertCard.java	0.00%	7 Missing :warning:
src/main/java/seedu/address/ui/MainWindow.java	0.00%	2 Missing :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...rc/main/java/seedu/address/logic/LogicManager.java	78.26% <100.00%> (+0.98%)	4.00 <1.00> (+1.00)
src/main/java/seedu/address/ui/PersonCard.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
src/main/java/seedu/address/ui/MainWindow.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
src/main/java/seedu/address/ui/ConcertCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...c/main/java/seedu/address/ui/ConcertListPanel.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)

... and 1 file with indirect coverage changes