LRDOCS-1385 Add Jgit JAR to liferay-docs lib and introduce taskdef and ant target
LRDOCS-1385 Create GitCompare class which lists new/modified files
LRDOCS-1385 Enable diffs to print to txt file
LRDOCS-1385 Enable argument input functionality by giving GitCompare the 'main' method (Also renamed to remove 'Task')
LRDOCS-1385 Make sure Git ignores the generated TXT file
LRDOCS-1385 Added time stamp and branches used for comparison in generated TXT file for user convenience
LRDOCS-1385 Create new ant target, which grabs files from TXT file and puts them into file array
LRDOCS-1385 Provide zipping functionality to dist-diffs task
LRDOCS-1385 Formatting and finishing touches on Git and Diffs targets
LRDOCS-1385 Do not attempt to zip up files that have been deleted
LRDOCS-1385 More convenient to have git branch read automatically instead of passing it as arg. Also, don't create zip file if there are no diffs
LRDOCS-1385 Add methods that scan for MD files and find images
LRDOCS-1385 Add modified/new image MD files
LRDOCS-1385 Refactor code and scan for all modified/new MD file images
IDs and numbering.
Merge branch 'git-ant-task' of https://github.com/codyhoag/liferay-docs into pr216-git-ant-task-b

Conflicts:
	build-site-common.xml
	lib/liferay-doc-utils.jar
Update class to new Markdown converter API, removing reference to old LiferayParser.Sidebar() method.
Add older.branch argument to GitCompare class and its target compare-with-older-branch
Fix to only add images that are referenced at ../../images
Modify dist-diffs target, removing the dependency on the compare branches target, adding a dependency to prepare-dist (to ensure adding .METADATA file to ZIP), and adding temporary inclusion of ALL image files in the ZIP.