Support for optional fractional part of a second

[PavelTrushkin]

i have reworked OFTime::setISOFormattedTime and modified OFDateTime::setISOFormattedDateTime

new parser is very simple - old school char by char state machine :) but it works

Thanks!

[jriesmeier]

Thank you for your contribution! Not sure whether we will apply the patch directly (or adjust it a little bit...) but in any case you'll be mentioned as the original author/contributor.

Since we currently have no time to check your patch in detail, I've added the following entry to DCMTK's issue tracker (so your proposed patch doesn't get lost): https://support.dcmtk.org/redmine/issues/895

[PavelTrushkin]

Thats okay let me know if i can help with the patch adaptation