xml-encoding values in sabredav error responses.

Fixes Issue #237
Merge pull request #311 from DeepDiver1975/1.6

xml-encoding values in sabredav error responses.
Bumped version and updated changelog.
Added phing as a dev dependency, and added a few new entries to
.gitignore
Disabling building of pear packages. Channel is down :(
Merge branch '1.6' into 1.7

Conflicts:
	.gitignore
	ChangeLog
	build.xml
	composer.json
	lib/Sabre/DAV/Version.php
Added a few entires to .gitignore
Set the release date.