Fix a number of findbugs and checkstyle flagged problems

Hi,

I ran a couple of static checkers on the vert.x code base to determine its current state. Based on that result, this is a pull request to fix some of the more obvious problems encountered. Most of these changes are small and style-related but there are a couple of significant fixes for e.g. resource leaks or charset encoding problems in here.

All of these problems were found by static analysis using findbugs, PMD, checkstyle and a couple of other tools.

With this patch applied, there are no more warnings from (admittedly very tame) checkstyle; the pmd and findbugs reports can be reviewed here: https://gist.github.com/hgschmie/8156275

If you want to rerun the tests yourself, you might need to apply the patches from this branch first: https://github.com/hgschmie/vert.x/tree/maven-build, as I drive them from a maven build. This branch contains a full maven build for the vert.x tree; it might require some slight tweaks for the test suite (I have not bothered to run it in total).