CSSlint tweak: we are okay with 'overqualified' elements; in fact, we want them.
fix CSSlint-reported issues and ensure the content in the 'extra header row' actually fills the cell (instead of being too large vertically)
rowmovemanager: dragstart should not return false when the drag should not commence using this plugin (another one may want to 'see' the dragstart event as well)
- getRowPosition(pos) can legally receive negative row number -1 (when data length = 0): adjust the assert; the code can handle this situation well already

- provide the cellExists() function as an API method

- use cellExists() where applicable

- gotoUp & gotoLeft: use the same do...while logic as the other gotoXYZ calls as the pattern should be the same for all.
Fix bug due to common JS pitfall (closures inside loops): see http://bonsaiden.github.io/JavaScript-Garden/#function.closures ('Closures inside loops') why this function factory is required.
slick.headerfilter is code identical to that of slick.headermenu. The real headerfilter resides in ext.headerfilter.js
- fixing a series of CClint, JSlint and JSCS reports, including duplicate declared functions, variables, one instance where 'i' was an implicit global due to a missing 'var' declaration

- all exceptions now throw an Error class instance

- grunt task 'compile' was created to help compile the CSS files from LESS at the correct position in the build sequence when running 'grunt'.
added an additional (preliminary) example file which will showcase custom overlays for cells, a headerless grid and accessing data via DataView methods for both formatting and editing purposes.
whitespace police raid
add JSON load/store server-side data provider page + support code (PHP). The code is buttoned down for security by restricting files to a single, dedicated directory and validating all input by feeding it through a JSON parser before saving to disk.