[DOC,FIX] Small fix to documentation.
[DOC,FEATURE] Adding validation for signature keywords.
[DOC,FIX] Fixing dox signatures.
[DOX,FIX] Fixing exception documentation.
[FEATURE] Allowing metafunctions in class @signature for now.
[DOC,FIX,INTERNAL] Not displaying empty "detailed description" sections.
[DOC] Adding optional validator for @section Remarks.

Often it is unintentional that the detailed description starts out with a
@section Remarks.
[INTERNAL] Ignoring temporary files in .gitignore.
Merge pull request #79 from holtgrewe/fix/dox_fixes

Fixes to dox system.