gradle base skeleton.
removed .gradle directory.
dummy DSTore interface.
not yet very fascinating.. we can store a hierarchical tree inside a flat hash map...
it's getting too late. not too much is working though.. (hashesaren't correclty updated when a child node is added.)
slowly getting somewhere..
now also store commits correctly.
implemented a very simple json backed file store. also commit() will now move the branch ahead, if working tree follows a branch.
refactored storage

- root commit id is no longer part of storage
- storage provides method to convert from external string representation to internal storage id
example implementation for a adapter type interface.
Merge branch 'master' of github.com:dc2f/dstore-java
do not store parent id into nodestorage.
do not use map to store children. children are a simple flat list.
started to add a generic child query adapter
added a way to retrieve children generically by property (which.. is still specific for 'name' because we can't store properties yet.)
added jsr305 libraries for @Nonnull and @Nullable annotations.
added basic support for properties, and store the name of nodes as property instead of as a special data type.
expose getPropery(String name) method on working tree node
exposed getProperties() on WorkingTreeNode
expose getProperties() in WorkingTreeNode interface