Improved knockout binding.

Shift + Click range selection improvements. Fixes #431.

Improves the initialization of the multiselect by waiting for other select related bindings to finish first.
Moved the subscription to other binder events to init so they aren't re-executed all the time.
Added support for value binding.
Added support for observable configuration properties.
Observable subscription rate-limited (by @IDisposable).
Simplified how selection changes are processed (simpler code, not sure about performance).

Merge branch 'fix_#431' of https://github.com/Tyf0x/bootstrap-multiselect into shift-select-improvement

-> Fixed a failure on test for #405 due to the code changes

-> Now able to select/deselect ranges
-> The range is based on the previously active checkbox. (i.e: the user clicks a checkbox no 1 then checkbox no 5. The interval will be [1,5].)
-> The range new state (selected or deselected) depends on the last option clicked new value. Example: If the checkbox is Shift-clicked and becomes selected, the whole range will be too.
-> Improved the range select speed tremendously by only notifying the select for the "change" event once the whole range finished changing and manually doing the selection or deselection.

-> See https://bugzilla.mozilla.org/show_bug.cgi?id=559506
-> Removed the javascript:void(0) href for anchor elements in the multiselect dropdown
-> Added a tabindex = 0 to keep the anchors focus-able
-> Added code to remove any text selection when using shift+click
-> Handles the checkbox selection manually when done using shift+click on its label

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