ldoc: add integer type param alias

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
core: open ioctx object; add read,write,close

Adds cluster:open_ioctx(pool) method and adds support for
rados_write, rados_write, and rados_ioctx_close functions.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>