Use native HtmlDecode
Use native HashSet
Trim down references
Merge pull request #253 from alfaproject/hashset

Use native HashSet
Merge pull request #254 from alfaproject/references

Trim down references
Merge pull request #252 from alfaproject/html_decode

Use native HtmlDecode
Minor italic fixes in translate
Update run_tabspace.bat after the HashSet.cs removal.
Avoid using ToCharArray
Merge pull request #255 from alfaproject/to_char_array

Avoid using ToCharArray
Formatting.
Dutch translation (nl-NL) corrected and updated