Added support for remote Xapian via TCP

Supply a (host, port) pair for HAYSTACK_XAPIAN_PATH to connect to a remote Xapian instance on tcp
Spelling error corrected
Don't check for Write access

When searching, only read access is needed, so don't check for write
Merge branch 'master' of https://github.com/aarcro/xapian-haystack into HEAD

Conflicts:
	xapian_backend.py

Resolved by merging remote updates for in memory DB with local changes for remote db