Re-use ssh connection

- Previously only re-using if no flags were supplied; now re-use also
  if it's just that stdout/stderr have custom capturing.
  Important for SshSensorAdapter.
issue 452 fixed JcloudsLocation override of groupId causes DnsNameValidator to fail in jclouds
"brooklyn-fullusername-uids" on those clouds which don't have short limits, added unit test
Add `MySqlNode.DATA_DIR` config key for specifying the location of the DB files
Specify correct --datadir option.
Test override of MySQL data location in integration test.
add a version history
default deployment is now to filesystem on cloudfronted developers-origin,
with profile for deploying to artifactory;
docs updated to show same (new) preferred download URLs
fix docs build for the case where we are building docs for the root
brooklyn-dist should be in a directory named for the current version, not hanging off the root
update download links and instructions to reflect dist archive structure,
and be a little bit clearer in general
pom updated to support deployment to sonatype
remove unused sections of pom
reorder profiles in pom (no changes)
created bogus empty java files for examples, so that javadoc artifact is created, and build is not rejected by maven central!
doc links updated to point at sonatype and maven central (in addition to cloudsoft)
removed use of properties for deploymentManagement, now deployment management is just in profiles
Merge pull request #448 from ahgittin/feature/versioned-docs

Feature/versioned docs
Merge pull request #443 from aledsage/fix/reuse-ssh-connection

Re-use ssh connection
Merge pull request #432 from alasdairhodge/mysql-data-location-config

Permit configuration of MySQL data directory