add a boolean orphan argument to BranchCreateOp to create a new orphan branch
Beware LsTreeOp can be given a ref name which has no commits yet
Beware CheckoutOp can be called when no commits are yet on the specified branch
remove dead and commented out code
fix bug introduced at 5d41bee3 where removing a tree resulted in an empty tree after a commit
set default cli app heap size to 1G
Encapsulate AbstractGeogitCommand's workingTree, refDatabase, and index.

This patch makes commands access the working tree, index, and ref database consistently
through CommandLocator and encapsulates the behavior in three protected getters
on AbstractCommandLocator. This way it doesn't matter (for commands and other code)
whether the CommandLocator comes from and hence no need to figure out if its a transaction
or not to get the working tree/index/refdb from different places.
make the datastore able to work against a specified branch