Fixed plink reader to handle multiple field separators

Plink files can be space or tab separated. This is not always consistent
within one file. The current default separates on both space and tab.
Fixed another plink reader field separator
Added default sep to MapFileReader
Answered question in comments
Merge pull request #276 from PatrickDeelen/master

Fixed plink reader to handle multiple field separators
Failed log
Merge pull request #284 from erwinwinder/master

Failed log
access entity explorer through 'stable URL'
fix the molgenis forms
edited validation script + convertor script GIDS
Merge pull request #285 from dennishendriksen/master

Access entity explorer with stable URL #1625
changed validator GIDS
Merge pull request #286 from RoanKanninga/master

changed validator GIDS + fixed the molgenis form