Update UI to match project UI mockup

[siddarth2824]

Updates that were made to the UI to match the UI mockup which can be viewed here:

1. Changed the layout of the elements
2. Changed the respective background colors to match the UI mockup
3. Changed the font styles of all the fonts
4. Added functionality to the tabs to switch windows by setting the relevant fxml file as the focused element in the main display placeholder
5. Added border radius to the result display box to match UI mockup
6. Added padding between each transaction card to match UI mockup

[ianyong]

Could you rebase to address merge conflicts before we start reviewing?

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@3e647c1). Click here to learn what that means.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##             master      #75   +/-   ##
=========================================
  Coverage          ?   67.95%           
  Complexity        ?      404           
=========================================
  Files             ?       78           
  Lines             ?     1323           
  Branches          ?      115           
=========================================
  Hits              ?      899           
  Misses            ?      393           
  Partials          ?       31           

Impacted Files	Coverage Δ	Complexity Δ
...a/ay2021s1_cs2103_w16_3/finesse/ui/CommandBox.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...a/ay2021s1_cs2103_w16_3/finesse/ui/MainWindow.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...021s1_cs2103_w16_3/finesse/ui/TransactionCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
..._cs2103_w16_3/finesse/ui/TransactionListPanel.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
..._cs2103_w16_3/finesse/ui/expense/ExpensePanel.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...s1_cs2103_w16_3/finesse/ui/income/IncomePanel.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)

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[ianyong]

LGTM!

[zhaojj2209]

LGTM!