Prevent line breaks in menu

Using CSS style white-space: nowrap; in menu, the long lists
no longer get dropped to the next line (wrapping behavior).
Instead, they are allowed to overlap out of the menu.
Change overflow-y from 'scroll' to 'auto'

The goal is to prevent the display of a scrollbar in the menu
(in the middle of the page) unless actually necessary:

   "The behavior of the ‘auto’ value is UA-dependent,
    but should cause a scrolling mechanism to be provided
    for overflowing boxes."
    -- description of value 'auto'
       in 11.1. The ‘overflow’, ‘overflow-x’ and ‘overflow-y’ properties
       in CSS basic box model (css3-box)
       http://www.w3.org/TR/css3-box/#overflow-x
Make selectedOptionText parameter optional in adjustSelectWidth

Providing the parameter avoids multiple DOM accesses, but calling
the function is now more straightforward when the selected text
is unknown.
Extract adjustSelectWidth() from filter-utils to select-utils

I plan to reuse the function in group-by-category.
Add named function for onchange event handler of group selection
Adjust width of group selection list as selected value changes
Make selectedOptionText parameter required in adjustSelectWidth

I prefer to avoid extra DOM access as much as possible.

This reverts commit 714dbd2
Use non-breaking space by default in padding
Use NBSP constant defined in string-utils
Add a non-breaking space for padding at end of option to measure

The padding applied to the select appears after the arrow.
This extra character introduces padding between the selected
option and the arrow.

The result is more consistent in Firefox / Safari than defining
some padding-right on the option element.
Update display of the selected grouping criteria, next to the list

I considered extracting a function for this common processing
from filter-utils to select-utils, but the call only was more
complex than the inline code.
On reset, expand former option before selecting default value

Otherwise, the selected value would appear in the reduced form
in the list of options...
Refactoring: inline function hideOptionWithNoAuthorSelected()
Never hide the default option

I assumed that there would always be at least 1 other matching
the default category for any filter, but I have now found
counterexamples: when no filter is selected except the total
contributions filter, any value above 8 included results in
no matching Assessment Report value: there is no author with
8 contributions in a single assessment report.

Likewise, the Role filter matches no author with 10 contributions
or more: no author has more than 10 contributions in a single role.
Update colors used for roles, with a ring for multiple roles
Display multiple working groups as rings too
Use red for WG 1+2+3, different colors for other working groups
Use buttons instead of a list to switch between Visualization and Data
Merge branch 'enhancements'
Merge branch 'master' into gh-pages