improve documentation of the options form in views_handler_filter

'1403188 by dereine: Choosing a filter with 'contains any word' but not providing a default word gives a SQL syntax error and 1326403441

This reverts commit 745eb654.

#1367304 by tim.plunkett, dereine: Allow to use arguments with multiple filter groups together. Therefore all filter groups get converted from 0,1 to 1,2 because 0 is made as a special group which has always AND which is then used by the arguments

#1387396 by twistor: The Preserve certain tags dependent field should be directly below the Strip HTML tags checkbox

#1137892 by agentrickard: Provide an area handler which allows to use some tokens(items per page, etc.) in the header/footer.

by dereine: Improve filter term_node by defining all used variables, removed unused variables and document much more stuff.

'#1333110 by sammyd56: Fix the description of the hide if empty checkbox. This was probably a leftover from first versions of the initial patch