Reverted changes meant for 2.0.0 and restored Java8 compatibility

[Lonzak]

1. Reverted be38865 to maintain compatibility with iText. This kind of changes will be done in 2.0.0 onwards.

2. Commit 63a678d broke java8 compatibility

[RadekWikturna]

Can you please fix the problems reported by Codacy?

[asturio]

Hi @Lonzak ,

if you have time take a look at my marking. If not, I can merge this and try to check if these are really ok, in a "cleanup" commit.

[asturio]

Looking tomorrow again, and merging.

[Lonzak]

I have to admit I didn't check the changes from the commit ( be38865) in detail - I just used the revert function of my git tool...
Parts of the changes like using isEmpty() and so on is of course better. And I would also remove the ITXT variable from PdfName...

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[Lonzak]

Ok I did commit the changes.

By the way: Should we do something about the failing test in

PdfDocumentCJKExtensionTest.generateDocumentsWithCJKExtension
fonts/TakaoMjFonts/TakaoMjMincho.ttf

The font is missing.
We should either comment the test with @ignore or add the font...

[asturio]

The code is not compiling. I think the given test class was removed.

The missing fonts are huge, so I would just delete the test or add an @disabled there.

[asturio]

I think for this PR the Codacy could be ignored.