fix(typeahead): fix loading callback when deleting characters

Closes #1140
fix(tooltip): hide tooltips when content becomes empty

Closes #875
feat(tooltip): add ability to enable / disable tooltip
fix(datapicker): set popup initial position in append-to-body case

Set the initial position offsets of the datepicker popup element in case of appended to 'body'.

Todo: refresh the position on parent elements resize.
feat(dropdownToggle): disable dropdown when it has the disabled class
chore(merge): merge branch 'master' into bootstrap3_bis2