Web Inspector: Shortcuts screen UI polish

Web Inspector: Shortcuts screen UI polish
https://bugs.webkit.org/show_bug.cgi?id=84708

  1) remove inconsistent shadow;
  2) reduce border radius;
  3) vertically center the “X” button;
  4) replace unreadable symbolic shortcuts with text;
  5) gaps / colors / opacity adjustments;
  6) section-to-column distribution algorithm is replaced with a fair one.

Patch by Eugene Klyuchnikov <eustas.bug@gmail.com> on 2012-04-28
Reviewed by Pavel Feldman.

This is a UI polising patch, so no new tests added.

* English.lproj/localizedStrings.js: added keyboars arrow keys items
* inspector/front-end/KeyboardShortcut.js: replace unreadable symbolic shortcuts with text
* inspector/front-end/ShortcutsScreen.js:
(WebInspector.ShortcutsScreen):
(WebInspector.ShortcutsScreen.prototype.show): remove redundant parameter
(WebInspector.ShortcutsScreen.prototype._buildTable): change section distributing algorithm
(WebInspector.ShortcutsSection.prototype.renderSection): render colon with margins
(WebInspector.ShortcutsSection.prototype._renderHeader): apply classname to th elements
* inspector/front-end/helpScreen.css:
(.help-window-main): reduce radius, remove shadow; tune color and opacity
(.help-window-caption): fix spacing; add ruler
(.help-window-title): fix spacing; remove ruler
(.help-content): fix spacing
(.help-close-button): fix spacing; adjust background color
(.help-column-table): fix spacing
(.help-table > tr > th): fix color
(.help-key): fix color
(.help-combine-keys, .help-key-delimiter): extract common style
(.help-combine-keys): remove dupe
(.help-section-title): add space between sections

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@115568 268f45cc-cd09-0410-ab3c-d52691b4dbfc