Extend Arlington to have FDF rules

[petervwyatt]

Feature request: extend Arlington to have FDF rules as per clause 12.7.8.

This might be possible using a new predicate e.g. fn:isFDF() which then alters fn:IsRequired, etc. in some way...
e.g. Size entry in FileTrailer is not required in FDF; and the FDF catalog dictionary is far simpler with less keys, Version key is different and an additional FDF key.

[petervwyatt]

• Length key of streams is required to be direct = fn:MustBeDirect(fn:IsFDF())
• %FDF-1.2 header
• make a new FDFCatalog.tsv for FDF files and alter FileTrailer.tsv so that Root Links field lists both Catalog and FDFCatalog (this is easier than making complicated predicates)
• new FDF.tsv for the FDF dictionary (Table 246)
• additional EncryptionRevision key in EmbeddedFileStream.tsv (Table 247)
• new FDFJavaScript.tsv for Table 248
• new FDFFieldDict.tsv for Table 249
• new FDFPageDict.tsv for Table 251
• new FDFTemplateDict.tsv for Table 252
• new FDFNamedPageReferenceDict.tsv for Table 253
• add integer Page key to all annotation dicts (Table 254) with fn:IsRequired(fn:IsFDF())