[DOC] Full doc comment for Page / Header / Title ViewHelper

Fixes: #122
[BUGFIX] Property "multiple" on Select ViewHelper is boolean

Fixes: #121
[BUGFIX] Set "multiple" on Select ViewHelper form argument, not tag attribute

This prevents any possible errors when using the "multiple" attribute by turning it into an argument rather than an attribute and manually setting/removing the actual tag attribute as needed.
Added new function getRenderedRecord to separate creating record content from query to fetch tt_content records
Added new arguments to abstract View Helper: render, using to returning array of tt_content records (render true, default)

Based on #81 FluidTYPO3/flux/issues
[FEATURE] Attribute "render" to return records, Content ViewHelper.