Adds merge_sort flag to unshard function.
Make things compile and fix a bug.
Adds a way to iterate a leaf node in reverse.
Change around gitignore files.
Pushes the direction down further.

Everything compiles here.
Make the unsharding work with opposite direction rgets.
Enables reverse streaming of table data.

This code is smoke tested but I'm still not 100% sure it's correct.
It's also not actually used right now so this commit should be fully
functional.
Adds the starts of a nicer iterator interface for leaf nodes.
Adds in the new iterator interface.

Also fixes several bugs that were causing rows to be dropped.
Refactors the rget unsharding function.
Move methods out of leaf_node_t.
++ and -- crash instead of noop on out-of-bounds.
Merge branch 'next' into merge_br

Conflicts:
	src/rdb_protocol/protocol.cc