Fixes #405

Updated documentation. In short: #380, #365, #381, #377, #385, #384, #388, #302, #305, #391, #374, #397, #400, #375, #383, #301, #382, #386, #387, #404.

#375, #383: Avoid changing unrelated parent elements.

Correct filtering with optgroups.

#374. Added optional clear button for filter feature.

#385, #384: titles for options, supporting dataprovider; dataprovider with preselected options.

Allow options to be defined by data attributes.

#305, #302. Added enableClickableOptGroups option.

Only deploy the necessary files with Bower.

#377. Allow enter in filter.

#365. Additional option for selectAll.

Factorise some code too

Add ability to handle the "caption" property from the dataprovider() to display a title on hover of each option label

Update doc

Use .closest() instead of .parents() because the latter will also reach parent elements of the plugin container

In other words, if the multiselect plugin is used inside an LI.container tag, it will eventually modify it which is not intended

Just set the 'selected' property to true on the data item
Works also for optgroup's options.

Also use jQuery tag constructor and attribute setter to avoid HTML filtering issues