Fixed issue #8161: (quexml-pdf) field lengths

Dev: multi-flexi array text and number questions now honor
Dev: maximum_chars attribute.
Dev: Short free text question: when no maximum_chars value
Dev: is given in attributes, field length defaults to 25, with values
Dev: values above 50 (two lines of text), a text box will be used
Dev: instead of the "form-type" text field.
Dev: LS 'short text' always translates to quexml 'text'

Dev: as discussed w/ @adamzammit
Dev:  at http://bugs.limesurvey.org/view.php?id=8161
Merge pull request #126 from mfaber/quexf_fieldlength205

Fixed issue #8161: (quexml-pdf) field lengths