Update to Checkstyle 5.6

Checkstyle 5.6 is the latest version at time of writing.  This change
updates the ant build to use version 5.6, and makes some minor changes
to the checkstyle configuration to avoid errors.
Update to newest versions of dependent libraries
Gradle master build scripts

Add primary Gradle build scripts.  Per-project scripts are not yet included.
Gradle build scripts for java projects

Configure all java projects with Gradle build scripts.
Remove eclipse project files

Remove eclipse project files because they are automatically generated by
gradle.
Update ignored files for gradle build

Exclude eclipse project files from git now that they're not managed in
source control.
No longer exclude several directories that were created by the ant
build.
Disable Checkstyle RedundantThrows check

The gradle build trips over on the Checkstyle RedundantThrows check due
to being unable to find the definition of exception classes.  This may
be due to the Gradle Checkstyle plugin not setting up the Checkstyle
classpath correctly.  This change disables the check to work around the
issue.
Gradle build script for package project

Configure the package project with a Gradle build script.
Add gradle wrapper

The gradle wrapper allows the build to be performed without requiring
gradle itself to be installed.  It handles downloading and bootstrapping
a gradle installation/environment prior to running the gradle build
itself.
Update README for gradle

Add gradle instructions to the main README.
Pass custom database properties to tests

The database unit tests rely on custom system properties to define the
location of the database authentication files.  This change updates the
gradle script to pass on these custom properties from the gradle runtime
to the unit tests in a similar way to how the ant build used to do it.
Update eclipse projects to match new library dependencies

The previous commit updated a number of dependency versions.  This
change aligns the eclipse project files with this change.
Merge remote-tracking branch 'origin/master' into gradle
Update gradle build to newest versions of dependent libraries

This change brings the dependencies in the gradle build up to the same
level as those used in the ant build.
Remove ant build

This change removes all files related to the ant build now that it has
been replaced by gradle.
Remove miscellaneous obsolete build files

Remove a number of old build files that have accumulated in the tree and
are now obsolete.  Most of these appear to be related to Maven build
support, but this has been out of date since the move to a multi-project plugin-
based structure.
Remove debian build support

The debian build scripts contained in this directory are obsolete and
haven't been updated since the move to a multi-project plugin-based
structure.
Merge remote-tracking branch 'origin/master'

Conflicts:
	apidb/.classpath
	areafilter/.classpath
	core/.classpath
	dataset/.classpath
	extract/.classpath
	hstore-jdbc/.classpath
	pbf/.classpath
	pgsimple/.classpath
	pgsnapshot/.classpath
	replication-http/.classpath
	replication/.classpath
	set/.classpath
	tagfilter/.classpath
	testutil/.classpath
	xml/.classpath