TIKA-1278: Expose PDF Avg Char and Spacing Tolerance Config Params
   - Added averageCharTolerance and spacingTolerance fields to PDFParserConfig
   - Moved configuration of PDF2XHTML params from PDF2XHTML.process to new PDFParserConfig.configure method

git-svn-id: https://svn.apache.org/repos/asf/tika/trunk@1589722 13f79535-47bb-0310-9956-ffa450edef68