refactor generate-combined.sh

Update the generate-combined.sh script to support printing an ordered
source file list, cat'ing the compressed or uncompressed output, or
updating the dygraph-combined.js file (the default). This is intended to
make it easier to integrate dygraphs code into other builds.

Move the plugins/{base,install}.js files to
dygraph-plugin-{base,install}.js, this simplifies the file list
by permitting use of plugins/*.js with no order dependency.
Merge pull request #198 from klausw-g/generate-refactor

refactor generate-combined.sh
move plugins/unzoom.js -> extras/unzoom.js
resize handler only added once per graph.
Resize event causes several event handlers to be be added. Make the events private, and prevent multiple registration.
use Dygraph.log in dygraphs.js
add advice about delaying dygraph instantiation when using excanvas.
Fix lint warnings.
Only print PASS when failed test count == 0. Or is that === 0?
Merge pull request #201 from kberg/lint-cleanse

Fix lint warnings.
Merge pull request #200 from kberg/resize-handler

Resize handler
Merge pull request #202 from kberg/tweak-tests

Only print PASS when failed test count == 0. Or is that === 0?
add broken test demo to show margin issues
Merge pull request #3 from danvk/master

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