Update Ui with sample data only

[jeannetoh99]

Ui is not yet linked with logic for now, but is viewable with sample data/stubs. Added SampleWanderlustDataUtil for testing. Also edited some of the VALIDATION_REGEX of classes under model as previous ones were not working as expected when tested.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@a5e8add). Click here to learn what that means.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##             master      #81   +/-   ##
=========================================
  Coverage          ?   38.01%           
  Complexity        ?      400           
=========================================
  Files             ?      121           
  Lines             ?     2336           
  Branches          ?      273           
=========================================
  Hits              ?      888           
  Misses            ?     1416           
  Partials          ?       32           

Impacted Files	Coverage Δ	Complexity Δ
...s/model/accommodation/UniqueAccommodationList.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...in/java/seedu/address/model/activity/Activity.java	0.00% <ø> (ø)	0.00 <0.00> (?)
.../java/seedu/address/model/activity/Importance.java	0.00% <ø> (ø)	0.00 <0.00> (?)
...edu/address/model/activity/UniqueActivityList.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...edu/address/model/activity/WanderlustDateTime.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...rc/main/java/seedu/address/model/commons/Cost.java	0.00% <ø> (ø)	0.00 <0.00> (?)
...rc/main/java/seedu/address/model/commons/Name.java	0.00% <ø> (ø)	0.00 <0.00> (?)
...va/seedu/address/model/commons/WanderlustDate.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...a/seedu/address/model/friend/UniqueFriendList.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...du/address/model/travelplan/AccommodationList.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
... and 12 more

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[lyeyixian]

LGTM. Just some minor things that I think can be changed