DDoc: file.d: Exceptions thrown (except slurp)

Added all missing Throws:, with the exception of slurp,
which might throw pretty much anything
(at least Exception, ErrnoException, ConvException, maybe FormatException, gave up on trying to parse all the called code
(main offenders are formattedRead and the File ctor)).
DDoc (minor): array.d: Appender.shrinkTo throws Exception

Specified that Exception gets thrown (the previous ddoc didn't make sense).
Merge pull request #1269 from kiith-sa/patch-4

DDoc (minor): array.d: Appender.shrinkTo throws Exception
Merge pull request #1268 from kiith-sa/patch-3

DDoc: file.d: Exceptions thrown (except slurp)