default ebean.properties with UTC timezone

[cwbriones]

Resolves #419.

See the issue for details. The short of it is that we already treat all unzoned times internally as UTC, mostly through the usage of Instant. Ebean by default however, uses the JVM timezone when it initializes its connection pool. This previously caused issues in tests, and so it was explicitly set to UTC there. This PR does the same by adding a default properties file.

[cwbriones]

My thought process in adding this default is that we're making this usage explicit, and by doing it through standard configuration anyone who's deployed mportal without configuring this can continue to do so by changing the timezone in ebean.properties

[cwbriones]

Alternatively - since this is properties file I might be mistaken in how easily overridden this is. If that's a problem I think we'll just have to resort to setting it ourselves in our deployment.

[cwbriones]

Closing since I think it's another source of configuration that could actually go out of sync (rather than a single source, the JVM's timezone). Additionally the prior issue seems mostly like a test isolation problem rather than one with the system during normal operation.