Drop mobile.png

No longer used with drop of pig
Merge pull request #473 from 1bigidea/drop-mobile

Drop mobile.png (last bit of cleanup) props Andrew
UI fix so that 'Buy Now Button only...' text isn't overlapped by the metabox.
Avoid PHP warnings by correctly providing defaults
Merge pull request #483 from leewillis77/tax_warning_fixes

Avoid PHP warnings by correctly providing defaults
basic JS to see about getting the display disabled when mandatory is checked
- simple toggle of display field

We should be always showing items that are mandatory and this just
enables a bit of UI switching to make that happen.
- getting all checkboxes and killing mandatory

Here is a stab at disabling the display checkboxes if mandatory is
already checked.
- fixing whitespace and adding docs

My editor on the other machine was doing screwy stuff with whitespace
and this is a fix.

Also thought a bit of explanation about what the code is doing is
warranted.
Version bump and readme update
Database Upgrade Routine to rename old _wpsc_* product metadata array keys so they no longer include the '_wpsc_' prefix

Fixes #492
Changelog for database upgrade routine
Stock and sale price empty values should be preserved.
1st pass
update
Fix PHP Notice.
Use wpsc_product_variation_price_from() instead of wpsc_product_variation_price_available()
Fix compatibility issues with the references to the wpsc-theme folder

- WPSC_THEME_ENGINE_V1_PATH and WPSC_THEME_ENGINE_V1_URL should be used to refer to the templates' paths.
- Restore the wpsc-theme folder, just in case old themes are still relying on these files being there.
make  an empty array so implode doesn't fail
add wpsc_purchase_log_csv hook so we can do fun stuff before a CSV download