Sample enhancements: Remove token cache file, add properties file

[Avery-Dunn]

Implements changes discussed in https://github.com/Azure-Samples/ms-identity-java-desktop/issues/6

• Removes the sample_cache.json file of dummy data, so that the sample only uses the in-memory token cache
• Adds an application.properties file, to demonstrate better code practices by not having the user hard-code properties in the main class of the sample

Also implements further changes discussed outside of https://github.com/Azure-Samples/ms-identity-java-desktop/issues/6

• Call the try/catch block with the acquireTokenSilently and acquireTokenUsernamePassword methods twice, so that it demonstrates the silent/not silent pattern fully: first what happens when acquireTokenSilently fails and needs to fall back on a flow-specific acquireToken call, and then what happens when acquireTokenSilently succeeds
• Add a function to filter the accounts based on user name, like an existing comment in the sample suggested the user does in a 'real' application

[sangonzal]

These changes should also be made in the samples included in the main repository. I would recommend waiting until we agree on the changes that are necessary before porting them.