Fix confidence computation and filtering

[ikiss-fit]

• Single function for confidence computation (with text) - compute in OCR engine - Copute character confidences and save with transcription in TextLine -- character confidence will be used only inside export_ALTO
• Run the same function at the end of PageParser and when loading data with logits - Remove Update_confidences after decoder in PageParser
• Use page parser parameter - filter_confident_lines_threshold to filter lines at the end of PageParser
• Remove confidence computation and filtering from ALTO export
• Move before ALTO export filtering in API code
• Use character confidences in ALTO EXPORT
• Add page leve confidence to PageLayout - compute it at the end of PageParser -- remove this computation from API - use this value in API.
• IMPORTANT - Create a TEST suite!!!!!!!!!!!!!!!!!!!!!!!!!!!!!