slidePresenter Code

merging in changes from 0.40-beta branch, which was released yesterday as 0.40-RC-1. General expectation is that this code will go basically unchanged to a stable release of 0.40, meaning I will release it unless some bugs are found, meaning this is now stable and only bug-fixes will be performed; therefore I'm putting it all in trunk.

data/db/meta.php: new file to contain data metadata
html/js/idrag.js: new file for jquery drag-drop
html/js/iutil.js: same
html/js/jquery.js: same
html/js/jquery-json.js: new file for jquery-json
inc/class/class.data_txt.php: changed the way data version is determined (using meta.php if possible)
inc/lang/en.php: added some new language strings related to upgrade features
inc/modules/viewUpgrades.php: partially written module for upgrade features
inc/modules/upgrade_0.40_.php: same
inc/prepend.php: added constant SLP_CODE_VERSION
inc/templates/viewUpgrades.tpl.php: new template for upgrade features