BuiltIn: Little doc cleanup.

- Use Unicode escapes instead of module level encoding with non-ASCII chars.
- Whitespace in examples.
INSTALL: Mention Py3 port also under Python installation section
UG: Clean-up tag pattern section in order to make it easier to add more content.
UG: Document that tags with AND/OR/NOT should be used as lower case with tag patterns.

Resolves issue #1845.
Removed old and totally outdated packaging instructions. BUILD.rst contains updated information.
rm outdated nsn icon
include packaging instructions and utilities in source distribution
tasks.py: Little code/doc cleanup
UG: Enhance suite init file docs.

Includes better explanation how to share kws/vars using resources files. Fixes #1851.