Reorganized examples into subdirectories.

To improve organization with the increasing number of examples, every
example page is now the index of its own subdirectory, which contains
all the files specific to that example.
Renamed layout.css to examples.css.
Beautified CSS used by the examples pages.

Slightly widened the page to account for the fact that most people have
widescreen monitors these days.  Also made text larger and more legible,
and created a nice 'clipping' effect for the placeholder.
Fix plot legend padding.

Added explicit border-spacing to compensate for global removal of
padding.  Flot should really take care of this itself; layout-critical
styles shouldn't depend on the user-agent defaults.
Expand buttons to match the new page font size.
Expand inputs to match the new page font size.
Generalize placeholder styles.

Give any direct child of demo-containre the same style, so it can be
used for both #placeholder and #overview.
Pad check boxes to match the new page font size.
Add a sub-header style for per-plot labels.
Re-styled and cleaned up all the examples.
Avoid being too specific in placeholder styles.
Additional code & comments cleanup.
Fix the pie interactivity example.
Flatten pie button styles so they fit in better.
Allow live resizing in the resize example.
Add the Flot version to each example's footer.
Update example index page links for nesting.
Updated examples index page styles.
Merge pull request #940 from dnschnur/better-examples

Revamped the built-in examples.