Remove sample data on startup

[thomastanck]

Resolves #156 by not having any initial data.

[coveralls]

Pull Request Test Coverage Report for Build 940

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.02%) to 91.273%

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Files with Coverage Reduction	New Missed Lines	%
src/main/java/seedu/address/MainApp.java	1	54.88%
<!--	Total:	1		-->

Totals
Change from base Build 929:	0.02%
Covered Lines:	2437
Relevant Lines:	2670

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💛 - Coveralls

[rlrh]

Should we have one entry so the UI doesn't look so barren? Since when it is inevitably selected, it gets downloaded anyway.

[qjqqyy]

Should we have one entry so the UI doesn't look so barren? Since when it is inevitably selected, it gets downloaded anyway.

Unfortunately that means we have to ship the jar with the data folder, or hardcode the entry's contents somehow. Or else the user can still start the application for the first time while offline and reproduce #156

[qjqqyy]

An alternative approach would be to start the sample entrybook with our user guide, which is accessible via jar:file:/path/to/README.jar!/docs/HelpWindow.html

[rlrh]

Should we have one entry so the UI doesn't look so barren? Since when it is inevitably selected, it gets downloaded anyway.

Unfortunately that means we have to ship the jar with the data folder, or hardcode the entry's contents somehow. Or else the user can still start the application for the first time while offline and reproduce #156

I see, I think it's better to remove the sample data then.