Asciidoc conversion

[rkratky]

What does this PR do?

Converts the entire bulk of docs from Markdown to Asciidoc(tor). The linked issue (#425) contains detailed explanation and reasoning for the conversion.

Jekyll is still used to generate the site, and the site's design and navigation elements are unchanged. I viewed every single page on the site to check for problems. If you find any, I'll fix them.

The PR includes:

• converted docs source files
• various fixes necessitated by invalid Markdown syntax
• updated Jekyll build system (run.sh, _config.yml, Gemfile)
• Dockerfile for building the image for local building & serving of the site (the image has also been pushed to Docker Hub, so no local building of the image is required; the run.sh script pulls this new image)

The only (quite minor) change is the syntax highlighter used for source-code listings. I couldn't get the currently used one (Rouge) to work, so I used a different one (Coderay). Syntax is still properly highlighted, only the colors used are a tiny bit different.

What issues does this PR fix or reference?

#425 (Convert docs to AsciiDoc)

[ghost]

@rkratky I can't find pom.xml in the PR - have you changed Docker image here too? https://github.com/eclipse/che-docs/blob/master/pom.xml#L68

[rkratky]

@eivantsov

I can't find pom.xml in the PR - have you changed Docker image here too? https://github.com/eclipse/che-docs/blob/master/pom.xml#L68

That I forgot. I will fix that. (What is it used for?)

[rkratky]

Apologies for the repeated push -- I keep forgetting to sign off on commits.

[ghost]

Well, this is a maven project, and docs are packaged as war artifact that is then packaged into Che server.

[slemeur]

+1 for the pom.xml

[rkratky]

Thanks, I updated pom.xml.

[ghost]

@rkratky can you please resolve conflicts and merge asap?

[rkratky]

@eivantsov Apologies for the delay, I was on PTO.

The conflicts are resolved, please merge.