Introduce basic checkstyle configuration

[gehel]

Style is now check during build at verify phase. Configuration is minimal and only checks for 2-space indentation at the moment. It can obviously be extended as required.

Build will fail if violations are found.

fixes #97

[gehel]

Let me know if you think this approach make sense for the project.

And let me know if you want me to rebase this on top of #96.

[chrisvest]

Looks like no rebasing is necessary.

Another rule I tend to follow is an 80 column line limit. Ideally that should only produce a warning, since there might be exceptions where longer lines are more pleasing to a human eye. I guess that could go into a separate PR if produces a lot of violations that should be checked over.

[gehel]

And I thought that everyone was using 120 or 130 as max line length those days ...

There are 30 violations on a line length of 80, 8 on a line length of 100 and none on a line length of 120.

Checkstyle does not have a mechanism to assign different priorities to different rules. I could configure checkstyle to run twice, with 2 different configurations, but I don't really like that option (files would be parsed twice...). Or configure checkstyle to only warn on violations for all rules.

My preferred option would be to configure a line length of 100 as a hard limit, correct the few places where that limit is violated and turn off checkstyle for the few places where it make sense to break that limit via inline comments.

[gehel]

I pushed another commit with line length configuration. I use stop checking line length and start checking line length as comment to mark code where we want to ignore this rule. I did some minor formatting corrections to ensure the rule is respected where it make sense.

Let me know if you want another configuration, or if you want me to squash those commits before merge.

[chrisvest]

This looks good. I think selectively turning line length checking off is a better solution than making them warnings. Makes it a conscious decision.