Fixed API doc related to Keyword.message
import and indentation fixes
Refactored XML element handling. Algorithm is now symmetric and easier to understand. Also error message as proper English.
ItemList: better error type and message when trying to slice
ItemList: additional utests
model: avoid creating (empty) lists when not necessary to save a little memory
ItemList: use tuples, not lists, as the backend storage, to save memory.

Tuples in general take a little less memory than lists because the latter reserve memory for possible elements to be added. The difference is biggest with empty tuples vs empty lists, because the former are implemented as singletons in Python.

A drawback of this change is that `list.append(item)` is a bit faster than `tuple += (item,)`. With short sequences the difference is insignificant, though, and most of the ItemLists are rather short.
model.keyword: Use intern to reduce memory footprint
Backed out changeset a07a37e43e48
Documentation enhancements to --RemoteKeywords NAME:<pattern>

Update issue 1480
Enhancements to --help and UG docs.
fixed typo in comment
rm incorrect statement from a docstring
Avoid deprecated has_key.

Udate issue 1479
Status: Started
Owner: pekka.klarck
Removed has_key in few places where they were used internally. Left few others that are in code that's going to be rewritten in the future anyway.
Collections: Proper English in error messages, idiomatic Python, etc. cleanup.
Collections: Don't use has_key because collections.Mapping does not have it.

Update issue 1479
Status: Done
Fixed with a test.
setup.py: support setuptools development mode

Update issue 1484
Status: Done
Owner: pekka.klarck
Fixed by importing setuptools when `develop` option is used.