add default configuration closure for downloading
add documentation for default download config
adds ssl self-signed cert. helper
example on how to accept self-signed certs
fix method name in documentation
accept all hostnames, not only localhost
Merge branch 'master' into accept-self-signed-certificates-helper
promote certificate handling to it's own section
Merge branch 'accept-self-signed-certificates-helper' of https://github.com/c089/geb

Conflicts:
	module/geb-core/src/main/groovy/geb/report/ReportState.groovy
Post merge cleanup.

- add tests for using self-signed certs and globally configuring connections in Download API
- change API of SelfSignedCertificateHelper to use URL for specifying keystore location
- mention new features in docs